Hot coffee: associative memory with bump attractor cell assemblies of spiking neurons

Networks of spiking neurons can have persistently firing stable bump attractors to represent continuous spaces (like temperature). This can be done with a topology with local excitatory synapses and local surround inhibitory synapses. Activating large ranges in the attractor can lead to multiple bumps, that show repeller and attractor dynamics; however, these bumps can be merged by overcoming the repeller dynamics. A simple associative memory can include these bump attractors, allowing the use of continuous variables in these memories, and these associations can be learned by Hebbian rules. These simulations are related to biological networks, showing that this is a step toward a more complete neural cognitive associative memory

Design and characterization of a biomimetic composite inspired to human bone

Many biological materials are generally considered composites, made of relatively weak constituents and with a hierarchical arrangement, resulting in outstanding mechanical properties, difficult to be reached in man-made materials. An example is human bone, whose hierarchical structure strongly affects its mechanical performance, toughness in particular, by activating different toughening mechanisms occurring at different length scales. At microscale, the principal toughening mechanism occurring in bone is crack deflection. Here, we study the structure of bone and we focus on the role of the microstructure on its fracture behaviour, with the goal of mimicking it in a new composite. We select the main structural features, the osteons, which play a crucial role in leading to crack deflection, and we reproduce them in a synthetic composite. The paper describes the design, manufacturing and characterization of a newly designed composite, whose structure is inspired to the Haversian structure of cortical bone, and that of a classic laminate developed for comparative reasons. We conclude with a critical discussion on the results of the mechanical tests carried out on the new composite and on the comparative laminate, highlighting strengths and shortcomings of the new biomimetic material

High-cycle fatigue strength of a pultruded composite material

Dealing with composites in polymeric matrix, the pultruded ones are among the more suitable for large production rates and volumes. For this reason, their use is increasing also in structural applications in civil and mechanical engineering. However, their use is still limited by the partial knowledge of their fatigue behaviour; in many applications it is, indeed, required a duration of many millions of cycles, while most of the data that can be found in literature refer to a maximum number of cycles equal to 3 millions. In this paper a pultruded composite used for manufacturing structural beams is considered and its mechanical behaviour characterized by means of static and high-cycle fatigue tests. The results allowed to determine the S-N curve of the material and to assess the existence of a fatigue limit. Observations at the scanning electronic microscope (SEM) allowed to evaluate the damage mechanisms involved in the static and fatigue failure of the material

SPATIAL AND TEMPORAL DYNAMICS OF ROOT REINFORCEMENT IN ALPINE FORESTS

Protection forests represent an effective tool to prevent and mitigate hydrogeological instabilities and are object of renewed interest in the European Alps, where there is a long history of cohabitation between people and natural hazards. The quantification of the effects of forests against the different types of natural hazards is however still a challenge, and represents a key step for the implementation of an integrated protection strategy able to combine engineering structures with forests. Forests provide different protection mechanisms depending on the type of natural hazards we consider. The aim of this work is to give a contribution to the quantification of the effects of forest vegetation against shallow landslides. Mechanical reinforcement of soil given by root systems is considered the most important contribution of alpine forests against shallow landslides. Many studies proved that it plays a key role in slope stability, but its quantification is still a challenge due to the huge variability that characterizes root reinforcement values. Understanding and modeling this variability is a key step in the development of stability models able to account for the role of vegetation, and to provide practical guidelines to foresters involved in the management of protection forests. Root mechanical reinforcement depends primarily on the density and distribution of roots of different diameter class (i.e. number and size of roots) and on their mechanical properties. Both these factors are subject to a huge variability in natural slopes. We can distinguish a spatial variability, due to the different environmental and stand characteristics that influence root systems development, and a temporal variability, due to the anthropic or natural disturbances that modify the forest stand and as consequence the root systems. The first section of this work presents a review on the role of forests against shallow landslides and the state of the art of the studies on root reinforcement, the models used for its quantification and its implementation in the stability models. The second section deals with the spatial variability of root reinforcement at both the regional and stand scale. The variability of root mechanical properties in several alpine species is analyzed basing on a wide data base obtained by laboratory tensile tests on roots coming from different forest sites in northern Italy, and a possible criterion for the interpretation and synthesis of this variability is proposed. The influence of both root mechanical properties and root distribution variability on the estimation of root reinforcement is then assessed in the case of a common alpine species, Picea abies, by means of the Root Bundle Model. Results show the importance of micro variability of root distribution at the stand scale that heavily affects root reinforcement estimation; the variability of root mechanical properties on the other hand cannot be ignored because it can lead to important errors in root reinforcement estimation. In the third section of the work the temporal dynamics of root reinforcement as consequence of logging activities are studied with intensive field work carried out in two different case of study, two mixed Silver fir \u2013 Norway spruce stands in the Italian Alps and four Norway spruce stands in the Swiss Alps. New experimental data for the quantification of root reinforcement decay after cutting for the selected species are provided, paying attention to both root mechanical properties and root distribution. A model for the estimation of root reinforcement decay that takes into account both the processes is proposed. Results show the importance of modeling horizontal root distribution in the study on root reinforcement decay and underline the need of further research on the role of natural regeneration in stabilizing gaps after cutting

Prolonged Nonhydrolytic Interaction of Nucleotide with CFTR's NH2-terminal Nucleotide Binding Domain and its Role in Channel Gating

CFTR, the protein defective in cystic fibrosis, functions as a Cl− channel regulated by cAMP-dependent protein kinase (PKA). CFTR is also an ATPase, comprising two nucleotide-binding domains (NBDs) thought to bind and hydrolyze ATP. In hydrolyzable nucleoside triphosphates, PKA-phosphorylated CFTR channels open into bursts, lasting on the order of a second, from closed (interburst) intervals of a second or more. To investigate nucleotide interactions underlying channel gating, we examined photolabeling by [α32P]8-N3ATP or [γ32P]8-N3ATP of intact CFTR channels expressed in HEK293T cells or Xenopus oocytes. We also exploited split CFTR channels to distinguish photolabeling at NBD1 from that at NBD2. To examine simple binding of nucleotide in the absence of hydrolysis and gating reactions, we photolabeled after incubation at 0°C with no washing. Nucleotide interactions under gating conditions were probed by photolabeling after incubation at 30°C, with extensive washing, also at 30°C. Phosphorylation of CFTR by PKA only slightly influenced photolabeling after either protocol. Strikingly, at 30°C nucleotide remained tightly bound at NBD1 for many minutes, in the form of nonhydrolyzed nucleoside triphosphate. As nucleotide-dependent gating of CFTR channels occurred on the time scale of seconds under comparable conditions, this suggests that the nucleotide interactions, including hydrolysis, that time CFTR channel opening and closing occur predominantly at NBD2. Vanadate also appeared to act at NBD2, presumably interrupting its hydrolytic cycle, and markedly delayed termination of channel open bursts. Vanadate somewhat increased the magnitude, but did not alter the rate, of the slow loss of nucleotide tightly bound at NBD1. Kinetic analysis of channel gating in Mg8-N3ATP or MgATP reveals that the rate-limiting step for CFTR channel opening at saturating [nucleotide] follows nucleotide binding to both NBDs. We propose that ATP remains tightly bound or occluded at CFTR's NBD1 for long periods, that binding of ATP at NBD2 leads to channel opening wherupon its hydrolysis prompts channel closing, and that phosphorylation acts like an automobile clutch that engages the NBD events to drive gating of the transmembrane ion pore

Effect of delamination on the fatigue life of GFRP: A thermographic and numerical study

Delamination is the major failure mechanism in composite laminates and eventually leads to material failure. An early-detection and a better understanding of this phenomenon, through non-destructive assessment, can provide a proper in situ repair and allow a better evaluation of its effects on residual strength of lightweight structural components. Here we adopt a joint numerical-experimental approach to study the effect of delamination on the fatigue life of glass/epoxy composites. To identify and monitor the evolution of the delamination during loading, we carried out stepwise cyclic tests coupled with IR-thermography on both undamaged and artificially-damaged samples. The outcome of the tests shows that IR-thermography is able to identify a threshold stress, named damage stress ?D, which is correlated to the damage initiation and the fatigue performance of the composite. Additionally, we performed FE-simulations, implementing the delamination by cohesive elements. Such models, calibrated on the basis of the experimental fatigue results, can provide a tool to assess the effect of parameters, such as the delamination size and location and composite stacking sequence, on the residual strength and fatigue life of the composite material

Mucopexy-Recto Anal Lifting (MuRAL) in managing obstructed defecation syndrome associated with prolapsed hemorrhoids and rectocele : preliminary results

Purpose: Treatment of rectocele associated with prolapsed hemorrhoids is a debated topic. Transanal stapling achieved good midterm results in patients with symptoms of obstructed defecation, nevertheless a number of severe complications have been reported. The aim of this study was to evaluate the safety and efficacy of a new endorectal manual technique in patients with obstructed defecation due to the combination of muco-hemorrhoidal prolapse and rectocele. Methods: Patients enrolled after preoperative obstructed defecation syndrome (ODS) score, defecography and anoscopy were submitted to the novel Mucopexy-Recto Anal Lifting (MuRAL) combined with a modified Block procedure, and followed up by independent observers with digital exploration 3 weeks postoperatively, and digital exploration plus anoscopy at 3, 6, and 12 months. Operative time, hospital stay, numerating rating scale (NRS), ODS, satisfaction scores, and recurrence rate were recorded. Results: Mean operative time was 35.7 minutes. Fifty-six patients completed 1-year follow-up: 7.1% had acute urinary retention, NRS score was < 3 from the third postoperative day, mean time of daily activity resumption was 12 days, none had persistent fecal urgency, 82% declared excellent/good satisfaction score, significant improvement of 6- and 12-month ODS score, no recurrence of rectocele, and 7.1% recurrence of prolapsed hemorrhoids were observed. Conclusion: MuRAL associated with modified Block technique gave no severe complications and resulted in a safe and effective approach to symptomatic rectocele associated with muco-rectal prolapse. Further randomized studies, larger series, and longer follow-up are needed. [Ann Surg Treat Res 2020;98(5):277-282

Mucopexy-recto anal lifting: a standardized minimally invasive method of managing symptomatic hemorrhoids, with an innovative suturing technique and the HemorPex System®

BACKGROUND: Conservative surgery of hemorrhoidal disease is less painful than traditional hemorrhoidectomy, and mucopexy has less risk of serious postoperative complications than stapled hemorrhoidopexy. The aim of this study was to evaluate the safety and effectiveness of a standardized, modified hemorrhoidopexy, named Mucopexy-Recto Anal Lifting (MuRAL) with the HemorPex System (HPS) in patients with symptomatic III and IV degree hemorrhoids. METHODS: Patients were enrolled from May 2013 to Dec 2015 and operated on with the MuRAL technique, based on arterial ligation and mucopexy at 6 locations, using a standardized clockwise/anti-clockwise rotation sequence of the HPS anoscope. Follow-up controls were carried out by independent observers, as follows: a digital exploration 3 weeks after the intervention, digital exploration plus proctoscopy at 3 and 12 months and repeated at a 12 months interval. Patients who did not strictly follow the postoperative controls were excluded from the study. Primary outcome measurement was the recurrence rate. Secondary measurements were: operative time, hospital stay, postoperative pain, postoperative symptoms and satisfaction score. RESULTS: We operated on 126 patients (72 males, mean age 53.9, range 29-83): 87 (69.6%) with III degree and 39 with IV degree hemorrhoids; 13 patients had a MuRAL as a revisional procedure of a previous operation for hemorrhoids. Mean duration of follow-up was 554 days (range 281-1219). Four patients were excluded from the study. One-year recurrence rate was 4.1%. The mean duration of the intervention was 29.5 minutes (range 23-60) and 92 patients (73%) were discharged during the same day of the operation. Pain VAS Score in the first, second and third postoperative day was 3.9, 2.5, and 1.9, respectively. Twenty-two patients (18%), all submitted to spinal anesthesia, had postoperative acute urinary retention. Fecal urgency, observed in 18.8% of patients at the first control, disappeared within one year after the operation. Mean time to return to normal activity was 8 days (range 5 -10). The patient satisfaction scores at one-year follow up were 31.1% excellent, 57.4% good, 7.4% fairly good and 4.1% poor. In patients with III degree hemorrhoids operative time was significantly shorter, postoperative pain better and transient fecal urgency lower than in IV degree patients. In our experience the standardization of MuRAL operation with HPS, turned out to be a safe and effective minimally invasive approach in managing symptomatic III and IV degree hemorrhoids, avoiding the risk of severe complications, with the possibility to perform a redo-MuRAL in the event of recurrence. CONCLUSIONS: In our series up to 88% of the patients reported a good, or excellent one-year satisfaction score. Further comparative randomized studies with longer follow-up period are needed