后巩膜加固术在高度近视性黄斑病变手术中的应用

近视性黄斑病变致盲率高,常用治疗手段为玻璃体切割术,然而单纯玻璃体切割术对于已出现严重后巩膜葡萄肿的超高度近视患者疗效欠佳。近年来临床应用玻璃体切割术联合后巩膜加固术治疗高度近视继发眼底病变,特别在黄斑劈裂及黄斑裂孔病例中,疗效肯定,前景可期。我们针对近年来后巩膜加固术的材料与术式变迁作一全面综述,并进一步讨论其应用于眼底手术中的发展远景。     

Cigarettes and alcohol: The influence of nicotine on operant alcohol self-administration and the mesolimbic dopamine system

Studies in human populations consistently demonstrate an interaction between nicotine and ethanol use, each drug influencing the use of the other. Here we present data and review evidence from animal studies that nicotine influences operant self-administration of ethanol. The operant reinforcement paradigm has proven to be a behaviorally relevant and quantitative model for studying ethanol-seeking behavior. Exposure to nicotine can modify the reinforcing properties of ethanol during different phases of ethanol self-administration, including acquisition, maintenance, and reinstatement. Our data suggest that non-daily intermittent nicotine exposure can trigger a long-lasting increase in ethanol self-administration. The biological basis for interactions between nicotine and ethanol is not well understood but may involve the stress hormone systems and adaptations in the mesolimbic dopamine system. Future studies that combine operant self-administration with techniques for monitoring or manipulating in vivo neurophysiology may provide new insights into the neuronal mechanisms that link nicotine and alcohol use.     

Effect of polyester fiber reinforcement on the mechanical properties of interim fixed partial dentures

Background

Different reinforcements currently available for interim fixed partial denture (FPD) materials do not provide the ideal strength for long-term use. Therefore, the aim of this investigation was to develop a more ideal provisional material for long-term use with better mechanical properties. This study evaluated the effectiveness of polyester fiber reinforcement on different interim FPD materials.

Methods

Thirty resin-bonded FPDs were constructed from three provisional interim FPD materials. Specimens were tested with a universal testing machine (UTM). The modulus of elasticity and flexural strength were recorded in MPa. The compressive strength and degree of deflection were calculated from the obtained values, and a two-way analysis of variance (ANOVA) was used to determine the significance.

Results

The polyester fiber reinforcement increased the mechanical properties. The modulus of elasticity for heat-polymerized polymethyl methacrylate (PMMA) was 624 MPa, compared to 700.2 MPa for the reinforced heat-cured sample. The flexural strengths of the bis-acrylic and cold-polymerized reinforced samples increased significantly to 2807 MPa and 979.86 MPa, respectively, compared to the nonreinforced samples. The mean compressive strength of the reinforced cold-polymerized PMMA samples was 439.17 MPa; and for the reinforced heat-polymerized PMMA samples, it was 1117.41 MPa. The degree of deflection was significantly greater (P < 0.05) in the reinforced bis-acrylic sample (5.03 MPa), compared with the nonreinforced bis-acrylic sample (2.95 MPa).

Conclusion

Within the limitations of this study, polyester fiber reinforcements improved the mechanical properties of heat-polymerized PMMA, cold-polymerized PMMA, and bis-acrylic provisional FPD materials.     

Evaluation of Hybrid Melamine and Steel Fiber Reinforced Geopolymers Composites

This study investigated the influence of the steel and melamine fibers hybridization on the flexural and compressive strength of a fly ash-based geopolymer. The applied reinforcement reduced the geopolymer brittleness. Currently, there are several types of polymer fibers available on the market. However, the authors did not come across information on the use of melamine fibers in geopolymer composites. Two systems of reinforcement for the composites were investigated in this work. Reinforcement with a single type of fiber and a hybrid system, i.e., two types of fibers. Both systems strengthened the base material. The research results showed the addition of melamine fibers as well as steel fibers increased the compressive and flexural strength in comparison to the plain matrix. In the case of a hybrid system, the achieved results showed a synergistic effect of the introduced fibers, which provided better strength results in relation to composites reinforced with a single type of fiber in the same amount by weight.     

Tensile Behavior of High-Strength,Strain-Hardening Cement-Based Composites (HS-SHCC) Reinforced with Continuous Textile Made of Ultra-High-Molecular-Weight Polyethylene

The paper at hand presents an investigation of the tensile behavior of high-strength, strain-hardening cement-based composites (HS-SHCC), reinforced with a single layer of continuous, two-dimensional textile made of ultra-high molecular weight polyethylene (UHMWPE). Uniaxial tension tests were performed on the bare UHMWPE textiles, on plain HS-SHCC, and on the hybrid fiber-reinforced composites. The bond properties between the textile yarns and the surrounding composite were investigated in single-yarn pullout experiments. In order to assess the influence of bond strength between the yarn and HS-SHCC on the tensile behavior of the composites with hybrid fiber reinforcement, the textile samples were analyzed both with, and without, an additional coating of epoxy resin and sand. Compared to the composites reinforced with carbon yarns in previous studies by the authors, the high elongation capacity of the UHMWPE textile established the higher strain capacity of the hybrid fiber-reinforced composites, and showed superior energy absorption capacity up to failure. The UHMWPE textile limited the average crack width in comparison with that of plain HS-SHCC, but led to slightly larger crack widths when compared to equivalent composites reinforced with carbon textile, the reason for which was traced back to the lower Young’s modulus and the higher elongation capacity of the polymer textile.     

Shear Performance of Reinforced Concrete Beams with Small Circular Openings Strengthened Using Rectangular and Octagonal-Shaped Reinforcement

An experimental case study was carried out to investigate the shear performance of reinforced concrete beams with small circular openings under a cyclic anti-symmetric bending moment. The openings were strengthened by using a newly developed reinforcement continuously bent into rectangular and octagonal shapes, which was convenient for installation and effective for crack control. The presence of web opening reinforcement, the reinforcing method, and the web opening spacing were employed as main variables in the design of five specimens. The cyclic performance of all specimens was evaluated in terms of failure mode, crack pattern, strength and stiffness degradation, and strain distribution. Experimental results were discussed to assess the suitability of the proposed web opening reinforcement in RC web opening beams. It was confirmed that the proposed web opening reinforcement exhibited outstanding crack control and served as a shear resistance component in place of the concrete cross-section lost due to web openings. Finally, the shear strength of all specimens, obtained from the cyclic loading tests, were compared with those obtained from the equation proposed by Mansur (1998) and the Architectural Institute of Japan standard 2010.     

Novelty exposure overcomes foot shock-induced spatial-memory impairment by processes of synaptic-tagging in rats

Novelty processing can transform short-term into long-term memory. We propose that this memory-reinforcing effect of novelty could be explained by mechanisms outlined in the "synaptic tagging hypothesis." Initial short-term memory is sustained by a transient plasticity change at activated synapses and sets synaptic tags. These tags are later able to capture and process the plasticity-related proteins (PRPs), which are required to transform a short-term synaptic change into a long-term one. Novelty is involved in inducing the synthesis of PRPs [Moncada D, et al. (2011) Proc Natl Acad Sci USA 108:12937-12936], which are then captured by the tagged synapses, consolidating memory. In contrast to novelty, stress can impair learning, memory, and synaptic plasticity. Here, we address questions as to whether novelty-induced PRPs are able to prevent the loss of memory caused by stress and if the latter would not interact with the tag-setting process. We used water-maze (WM) training as a spatial learning paradigm to test our hypothesis. Stress was induced by a strong foot shock (FS; 5 × 1 mA, 2 s) applied 5 min after WM training. Our data show that FS reduced long-term but not short-term memory in the WM paradigm. This negative effect on memory consolidation was time- and training-dependent. Interestingly, novelty exposure prevented the stress-induced memory loss of the spatial task and increased BDNF and Arc expression. This rescuing effect was blocked by anisomycin, suggesting that WM-tagged synapses were not reset by FS and were thus able to capture the novelty-induced PRPs, re-establishing FS-impaired long-term memory.     

BEHAVIORAL EXCESSES IN DEPRESSION: A LEARNING THEORY HYPOTHESIS

This paper reviews two learning theory‐based models of experiential contributions to depression: response contingent positive reinforcement and learned helplessness. The authors argue that these models connect to a phenomenon that may explain why symptoms of behavioral excess (e.g. rumination) often occur in depression that is otherwise marked by symptoms of behavioral deficit (e.g. anhedonia). Specifically, the authors illustrate that that concept of schedule strain (or low rates of response contingent reinforcement giving rise to low frequencies of behavior) unites these models. Depression is more likely, or more severe, when schedule strain conditions occur in situations containing reinforcers important to the individual and/or when they simultaneously occur in a number of situations. Conditions of schedule strain are known to give rise to adjunctive behaviors: apparently irrelevant, easy behaviors that deliver immediate reinforcement. This paper suggests that, for some depressed individuals, behavioral excess symptoms like rumination and overeating might serve adjunctive functions. Implications of this hypothesis are discussed.     

Variety of Self-Injury: Is the Number of Different Methods of Non-Suicidal Self-Injury Related to Personality,Psychopathology, or Functions of Self-Injury?

This study explored the association between number of methods of Nonsuicidal Self-Injury (NSSI) and personality, psychopathology, and functions of NSSI. Two combined undergraduate samples reporting a history of NSSI (n = 149) completed measures of personality, psychopathology, and NSSI. A series of regression analyses indicated that Conscientiousness, Openness, and two functions of NSSI (i.e., Automatic Negative Reinforcement and Social Negative Reinforcement) shared significant relationships with the number of NSSI methods participants engaged in. These findings demonstrate that, after accounting for NSSI frequency, a relationship exists among specific personality factors, NSSI functions, and engagement in additional methods of NSSI.