Fracture Load of 3D-Printed Interim Three-Unit Fixed Dental Prostheses: Impact of Printing Orientation and Post-Curing Time.

The fracture resistance of 3-unit interim fixed dental prostheses (IFDPs) fabricated using digital light processing (DLP) additive technology with different printing parameters is neglected. Therefore, this study investigates the effect of different printing orientations and different post-curing times on the fracture resistance of 3-unit IFDPs fabricated from two three-dimensional (3D) printed resins, NextDent, C&B (CB), ASIGA, and DentaTOOTH. A 3-unit dye was scanned, and an IFDP was designed. A total of 300 specimens (150/materials, n = 10) were printed and divided into three groups according to printing orientations (0°, 45°, 90°) per material. Each orientation was subdivided into five groups (n = 10) considering the post-curing time (green state as control, 30, 60, 90, and 120 min). All specimens underwent thermocycling (5000 cycles). Each specimen was fitted onto the die and loaded until fracture using a universal testing machine with a loading rate of 1 m/min. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05). The result showed that printing orientation had a significant effect on the fracture load for both ASIGA and NextDent materials (p < 0.05). The highest fracture load was recorded with 45° orientation, followed by 0° orientation and 90° orientation showed the lowest values per respective post-curing time. Post-curing time increased the fracture load (p < 0.05). Post-curing time had a positive effect on the fracture load. As the post-curing time increased, the fracture resistance load increased (p < 0.05), with 90 and 120 min showing the highest fracture load. The 0° and 45° printing orientations have a high fracture load for 3D-printed IFDPs, and an increased post-curing time is recommended.

A meta-analysis: The mortality and severity of COVID-19 among patients with mental disorders.

Several observational studies investigated the relationship between pre-diagnosis with mental disorders and COVID-19 outcomes. Thus, we have decided to conduct this meta-analysis to explore this relationship. We complied to the PRISMA guidelines in conducting this meta-analysis. PubMed, ScienceDirect, Google Scholar and medRxiv were searched until the 15th of February, 2021. We used the Random effect model in Meta XL, version 5.3 to pool the included studies. Statistical heterogeneity was assessed using Cochran's Q heterogeneity test and I². This meta-analysis included 634,338 COVID-19 patients from 16 studies. Our findings revealed that pre-diagnosis with mental disorders increased the risk of COVID-19 mortality and severity. This increase in the risk of COVID-19 mortality and severity remained significant in the model that only included the studies that adjusted for confounding variables. Furthermore, higher mortality was noticed in the included studies among schizophrenia, schizotypal and delusional disorders patients compared to mood disorders patients. In this meta-analysis we provided two models which both reported a significant increase in the risk of  COVID-19 severity and mortality among patients with mental disorders, and with the upcoming COVID-19 vaccines, we recommend to give this category the priority in the vaccination campaigns along with medical health providers and elderly.

The Synthetic Experiment: E. B. Titchener's Cornell Psychological Laboratory and the Test of Introspective Analysis.

Beginning in 1 9a0, a major thread of research was added to E. B. Titchener's Cornell laboratory: the synthetic experiment. Titchener and his graduate students used introspective analysis to reduce a perception, a complex experience, into its simple sensory constituents. To test the validity of that analysis, stimulus patterns were selected to reprodiuce the patterns of sensations found in the introspective analyses. If the original perception can be reconstructed in this way, then the analysis was considered validated. This article reviews development of the synthetic method in E. B. Titchener's laboratory at Cornell University and examines its impact on psychological research.

Combined local and systemic antibiotic delivery improves eradication of wound contamination: An animal experimental model of contaminated fracture.

Systemic antibiotics reduce infection in open fractures. Local delivery of antibiotics can provide higher doses to wounds without toxic systemic effects. This study investigated the effect on infection of combining systemic with local antibiotics via polymethylmethacrylate (PMMA) beads or gel delivery. An established Staphylococcus aureus contaminated fracture model in rats was used. Wounds were debrided and irrigated six hours after contamination and animals assigned to one of three groups, all of which received systemic antibiotics. One group had local delivery via antibiotic gel, another PMMA beads and the control group received no local antibiotics. After two weeks, bacterial levels were quantified. Combined local and systemic antibiotics were superior to systemic antibiotics alone at reducing the quantity of bacteria recoverable from each group (p = 0.002 for gel; p = 0.032 for beads). There was no difference in the bacterial counts between bead and gel delivery (p = 0.62). These results suggest that local antibiotics augment the antimicrobial effect of systemic antibiotics. Although no significant difference was found between vehicles, gel delivery offers technical advantages with its biodegradable nature, ability to conform to wound shape and to deliver increased doses. Further study is required to see if the gel delivery system has a clinical role.

Metal nanocluster light-emitting devices with suppressed parasitic emission and improved efficiency: exploring the impact of photophysical properties.

Here we investigate the photophysical properties of Au(0)@Au(i)-thiolate nanoclusters by controlling the degree of aggregation, and measure electrochemical energy levels to design a metal nanocluster-based thin film LED (MNC-LED) structure. These efforts allow us to implement MNC-LEDs with luminance exceeding 40 cd m(-2) and external quantum efficiency exceeding 0.1% with clearly visible orange emission. It is also demonstrated that by varying the sizes of nanoclusters, the electroluminescence spectrum of the device can be tuned to the infrared emission, indicating the possibility of exploiting metal nanocluster emitters for use over a wide spectral range.

A versatile model of open-fracture infection : a contaminated segmental rat femur defect.

OBJECTIVES: The purpose of this study was to refine an accepted contaminated rat femur defect model to result in an infection rate of approximately 50%. This threshold will allow examination of treatments aimed at reducing infection in open fractures with less risk of type II error. METHODS: Defects were created in the stablised femurs of anaethetised rats, contaminated with Staphylococcus aureus and then debrided and irrigated six hours later. After 14 days, the bone and implants were harvested for separate microbiological analysis. This basic model was developed in several studies by varying the quantity of bacterial inoculation, introducing various doses of systemic antibiotics with and without local antibiotics. RESULTS: The bacterial inoculation associated with a 50% infection rate was established as 1 × 10(2) colony forming units (CFU). With an initial bacterial inoculum of 1 × 10(5) CFU, the dose of systemic antibiotics associated with 50% infection was 5 mg/Kg of cafazolin injected sub-cutaneously every 12 hours, starting at the time of the first debridment and continuing for 72 hours (seven doses). The systemic dose of cafazolin was lowered to 2 mg/Kg when antibiotic polymethyl methacrylate beads were used concurrently with the same amount of bacterial inoculation. CONCLUSION: This model of open fracture infection has been further refined with potential for local and systemic antibiotics. This is a versatile model and with the concepts presented herein, it can be modified to evaluate various emerging therapies and concepts for open fractures. Cite this article: Bone Joint Res 2014;3:187-92.

Delocalization and dielectric screening of charge transfer states in organic photovoltaic cells.

Charge transfer (CT) states at a donor-acceptor heterojunction have a key role in the charge photogeneration process of organic solar cells, however, the mechanism by which these states dissociate efficiently into free carriers remains unclear. Here we explore the nature of these states in small molecule-fullerene bulk heterojunction photovoltaics with varying fullerene fraction and find that the CT energy scales with dielectric constant at high fullerene loading but that there is a threshold C60 crystallite size of ~4 nm below which the spatial extent of these states is reduced. Electroabsorption measurements indicate an increase in CT polarizability when C60 crystallite size exceeds this threshold, and that this change is correlated with increased charge separation yield supported by CT photoluminescence transients. These results support a model of charge separation via delocalized CT states independent of excess heterojunction offset driving energy and indicate that local fullerene crystallinity is critical to the charge separation process.

Translational research to improve the treatment of severe extremity injuries.

OBJECTIVES: Severe extremity injuries are the most significant injury sustained in combat wounds. Despite optimal clinical management, non-union and infection remain common complications. In a concerted effort to dovetail research efforts, there has been a collaboration between the UK and USA, with British military surgeons conducting translational studies under the auspices of the US Institute of Surgical Research. This paper describes 3 years of work. METHODS: A variety of studies were conducted using, and developing, a previously validated rat femur critical-sized defect model. Timing of surgical debridement and irrigation, different types of irrigants and different means of delivery of antibiotic and growth factors for infection control and to promote bone healing were investigated. RESULTS: Early debridement and irrigation were independently shown to reduce infection. Normal saline was the most optimal irrigant, superior to disinfectant solutions. A biodegradable gel demonstrated superior antibiotic delivery capabilities than standard polymethylmethacrylate beads. A polyurethane scaffold was shown to have the ability to deliver both antibiotics and growth factors. DISCUSSION: The importance of early transit times to Role 3 capabilities for definitive surgical care has been underlined. Novel and superior methods of antibiotic and growth factor delivery, compared with current clinical standards of care, have been shown. There is the potential for translation to clinical studies to promote infection control and bone healing in these devastating injuries.

The "silver-nitrate-oma".

This case report demonstrates and emphasises the unusual radiographic appearance of silver nitrate treatment in a 30-year-old patient, who subsequently underwent excision biopsy of a presumed potentially malignant lesion.

Electronic property investigations of single-walled carbon nanotube bundles in situ within a transmission electron microscope: an evaluation.

We have evaluated a combined transmission electron microscopy (TEM)-scanning tunnelling microscopy (STM) (hence TEM-STM) sample holder for the investigation of the mechanical and electrical properties of individual bundles of single-walled carbon nanotubes (SWCNTs) together with their simultaneous observation, analysis and mechanical modification in the TEM. Current-voltage (I-V) measurements from bundles of SWCNTs were observed to change as the bundles were deformed both reversibly and irreversibly, although the observed behaviour was somewhat complex. Electron energy loss spectroscopy (EELS) analysis revealed measurable changes in the bonding of the carbon atoms within the graphene layers upon bundle deformation, with measurable changes in the pi*/(pi*+sigma*) peak ratios observed at the carbon K-edge. Reversible deformation of the bundles was consistent with the sensitivity of sigma bonding to deviations from nonplanarity, whereas irreversible deformation was consistent with the introduction of nonhexagonal defects into the graphene sheets.

The experimental psychology of attitude change and the tradition of classical rhetoric.

Social psychologists might be surprised to learn that their discipline has been cut off from a vast and ancient family tree. The study of attitude change in the context of experimental social psychology began around 1918. It developed into a defined discipline in the 1930s and 1940s, particularly through the work of Carl Hovland and his associates. Unlike earlier specialties in experimental psychology, social psychology emerged well after the 19th-century split between psychology and philosophy in college curricula. Before this period of growth in empirical teaching and practice, the study of persuasion in classical rhetoric was a bedrock of higher education for more than 2000 years. Because of social psychology's late development in empirical science, there is a historical disconnect between experimental social psychology and its ancient philosophical counterpart, classical rhetoric. This article demonstrates similarities and differences between Hovland's findings and the theoretical groundings of classical rhetoric. We suggest areas where modern social psychology might benefit from a look at the older, more holistic theories of the art of rhetoric.

Carbon-carbon composite bearing materials in hip arthroplasty: analysis of wear and biological response to wear debris.

Ultra-high molecular weight polyethylene wear particles have been implicated as the major cause of osteolysis, implant loosening and late aseptic failure in total hip arthroplasties in vivo. This study initially screened 22 carbon-carbon composite materials as alternatives for UHMWPE in joint bearings. New bearing materials should satisfy certain criteria--they should have good wear properties that at least match UHMWPE, and produce wear particles with low levels of cytotoxic and osteolytic activity. Initial screening was based on wear resistance determined in short-term tribological pin-on-plate tests. Three materials (HMU-PP(s), HMU-RC-P(s), and SMS-RC-P(s)) which had superior wear resistance were selected for long-term testing. All materials had very low wear factors and SMS-RC-P(s), which had a wear factor of 0.08 +/- 0.56 x 10(-7) mm3/Nm, was selected for the subsequent biological testing and particle size analysis. SMS-RC-P(s) showed good biocompatibility in bulk material form and also the wear particles had low cytotoxicity for L929 fibroblasts in culture compared to metal wear particles. Wear debris size analysis by transmission electron microscopy showed that the particles were very small, with the vast majority being under 100 nm in size, similar to metal wear particles. The potential osteolytic effect of SMS-RC-P(s) wear particles was investigated by culturing particles with human peripheral blood mononuclear cells and measuring TNFalpha production. SMS-RC-P(s) did not significantly stimulate TNFalpha production at a particle volume to cell number ratio of 80:1, indicating that the debris had a low osteolytic potential. The results of this study suggest that carbon-carbon composites, particularly those composed of PAN-based fibers may be important biomaterials in the development of next generation bearing surfaces for use in total joint replacements that have very low wear rates and reduced osteolytic and cytotoxic potential.

Biological response to wear debris generated in carbon based composites as potential bearing surfaces for artificial hip joints.

UHMWPE wear particles have been implicated in osteolysis, implant loosening, and long-term failure of total hip arthroplasties in vivo. This study examined four carbon-based composite materials as alternatives for UHMWPE in joint bearings. These materials were HMU-CVD, SMS-CVD, P25-CVD, and CFR-PEEK. New bearing materials should satisfy certain criteria: they should have good wear properties that at least match UHMWPE, and produce wear particles with low levels of biological activity. Of the four materials tested in multidirectional pin-on-plate tribological tests, SMS-CVD, P25-CVD, and CFR-PEEK showed lower volumetric wear factors than UHMWPE. P25-CVD had the lowest wear factor of 0.54 +/- 0.34 x 10(-7) mm(3)/Nm. Analysis of P25-CVD wear particles by transmission electron microscopy showed that the debris was very small, with the vast majority of particles being under 100 nm in size, which was similar in size to metal wear particles. The P25-CVD particles were isolated and cultured with L929 fibroblasts and U937 monocytic cells to assess their effect on cell viability. P25-CVD particles were significantly less cytotoxic (p < 0.01, ANOVA) to both cell types than CoCr metal wear particles. This work suggests that carbon-carbon composite materials may have potential for use in total hip replacement bearings. Of the materials tested P25-CVD had the lowest wear factor, and produced very small wear debris that had minimal cytotoxic effect on L929 and U937 cells in vitro. Therefore carbon-carbon composites, such as P25-CVD, may be important in the development of next-generation implants with lower wear rates and reduced cytotoxic potential.

Georg von Békésy: visualization of hearing.

Georg von Békésy received the Nobel Prize in 1961 for his research on the functioning of the auditory system. In psychoacoustics, Békésy both extended and perfected the lines of research begun by von Helmholtz in the 19th century. First in his native Hungary and later at Harvard, Békésy used novel and imaginative devices and methods to observe and model the functioning of the inner ear. He also explored the nature of sensory inhibition by which the nervous system sharpens sensory transitions.

Quantitative valence plasmon mapping in the TEM: viewing physical properties at the nanoscale.

Using a series of graphitising carbons heat treated at different temperatures, the peak position of the bulk (pi+sigma) plasmon was measured using electron energy loss spectroscopy and observed to shift between 22 and 27eV. Experimental data is presented and discussed showing the effects of the collection conditions and sample orientation upon the observed spectra. We present an empirical technique by which quantitative energy filtered transmission electron microscopy (EFTEM) maps with two energy windows selected in the plasmon region can be readily acquired and processed, the results of which may be interpreted as graphitisation maps and subsequently physical property maps. An experimentally established resolution of approximately 1.6nm makes this technique a very useful tool with which to examine nanoscale properties in microstructural regions of interest in TEM specimens such as fibre/matrix interfaces within carbon-carbon composites, multi-walled carbon nanotubes and graphitic inclusions in carbon steels. Also presented is data demonstrating the unsuitability of pi(*)-related chemical EFTEM maps in both the low-loss region and at the carbon K ionisation edge for mapping bonding in such highly anisotropic media due to the strong orientation dependence of the intensity of the transitions involved. This is followed by suggestions for wider application of the plasmon mapping technique within systems other than those based upon carbon.

The virtual laboratory: a new on-line resource for the history of psychology.

The authors provide a description of the Virtual Laboratory at Department III of the Max Planck Institute for the History of Science in Berlin. The Virtual Laboratory currently provides Internet links to rooms that present texts, instruments, model organisms, research sites, and biographies. Existing links provide access to a library of journals, handbooks, monographs, and trade catalogues; research institutes and laboratories; biographies and bibliographic essays; and essays by contemporary researchers. Historians of psychology are encouraged to submit photographic material and essays to the Virtual Laboratory.

Study of carbon fibres and carbon-carbon composites by scanning thermal microscopy.

Scanning thermal microscopy (SThM) is a relatively new technique based on atomic force microscopy in which the tip is replaced by an ultra-miniature temperature probe. This paper reports on a preliminary investigation of the application of SThM in the characterization of the thermal properties of carbon fibres and carbon-carbon (CC) composites. The technique enabled a comparative study to be made of discrete fibre and matrix thermal properties in a series of model unidirectional composites. The thermal images revealed a marked increase in thermal conductivity of the matrix with increasing temperature of treatment and hence confirmed the development of a highly ordered carbon matrix. The results were in qualitative agreement with previously determined values of thermal conductivity from which the separate values of fibre and matrix thermal conductivity had been derived. The technique was also applied to the characterization of samples of unknown processing history, enabling an estimation to be made of the heat treatment and type of the fibres and matrix present in the composite. It was concluded that SThM promises to be a powerful technique for the study of the thermal properties of CC composites and carbon fibres, as it uniquely enables variations in local thermal conductivity to be detected and resolved. Absolute quantification of the technique remains the key to its future widespread acceptance in materials characterization.

Characterization of the fibre-matrix interfacial structure in carbon fibre-reinforced polycarbosilane-derived SiC matrix composites using STEM/EELS

This paper presents a characterization study of the microstructural evolution of various carbon fibre-reinforced polycarbosilane (PCS)-derived SiC matrix composites during high temperature heat treatment. Both surface-treated and untreated carbon fibre reinforcements were investigated. The STEM/EELS technique was found to be a particularly useful characterization tool. The results of quantitative EELS linescans have been interpreted in terms of the migration of gaseous SiO and CO, produced by the reaction between the small amount of SiO2 and excess carbon within the PCS-derived SiC matrix, from the central matrix region towards the fibre-matrix interfaces. Generally, the migration of gaseous SiO and CO results in an enrichment of SiO2 at the region adjacent to the fibre-matrix interface. However, differing final composite microstructures are formed depending on the strength of the fibre-matrix bonding. In the case of strong fibre-matrix interfacial bonding where few escape channels are present, a distinct Si-C-O layer was identified within the matrix adjacent to the fibre-matrix interface; both crystalline beta-SiC and the segregated Si-O-C phase coexist in this microstructure up to at least 1450 degrees C. In the case of weak fibre-matrix bonding this oxygen segregated interfacial layer is eventually removed at high enough temperatures. The final interfacial microstructure has important consequences for the mechanical properties of the composite material.