Retention Length Research Articles

Ventilation Dependency after Cardiac Operation for Infective Endocarditis: Risk Factors and Focus on Preoperative Aortic Regurgitation

Introduction: The investigation was to elucidate predictors of ventilation dependency after cardiac operation for infective endocarditis. Methods: Patients with infective endocarditis undergoing cardiac operation were retrospectively investigated. Mechanical ventilation >72 hours was defined as ventilation dependency after cardiac operation. Results: 896 patients with infective endocarditis who underwent cardiac operation were assigned to group of mechanical ventilation ≤72 h (n = 704) and >72 h (n = 192). Multivariate analyses identified age, interval from symptoms to operation, vegetation size, aortic occlusion length, pump length, intensive care unit (ICU) retention length, serum creatinine before and 24 h after surgery, preoperative and postoperative left ventricular end diastolic dimension (LVEDD), preoperative aortic regurgitation and packed red blood cells to be associated with ventilation dependency after cardiac operation; ventilation dependency is significantly related to prolonged ICU stay (>3 d), 1- and 5-year mortality after cardiac operation. All-time mortality (45.3% versus 5.6%, p < 0.001) of mechanical ventilation >72 h group was higher than that of mechanical ventilation ≤72 h group. A significant positive correlation exists between preoperative aortic regurgitation and ventilation dependency after cardiac operation. A value of preoperative aortic regurgitation >5.25 cm2 was 100% sensitive and 64.6% specific for the diagnosis of ventilation dependency after cardiac operation. Conclusions: We found modifiable risk factors of ventilation dependency after cardiac operation including interval from symptoms to operation, vegetation size, aortic occlusion length, pump length, ICU retention length, serum creatinine before and 24 h after operation, preoperative and postoperative LVEDD, preoperative aortic regurgitation and packed red blood cells and optimization of pre-, peri-, and postoperative factors that can reduce incidence of ventilation dependency, contributing to better short- and long-term outcomes.

Assessing Codend Mesh Selectivity: Comparing Diamond and Square Mesh Codend in the Red Sea Shrimp Trawl Fishery of Saudi Arabia

This study assessed catch composition, size selectivity, and fishing efficiency of demersal trawls targeting penaeid shrimp species in the Red Sea. It first compared the currently used diamond mesh codends in two fishing areas, Al Qunfudhah and Jazan, and then compared alternative square mesh codends to diamond mesh codends in Jazan. A total of 33 valid hauls were conducted in 2023, yielding 10,869 kg of total catch. The results showed that the square mesh codend significantly improved size selectivity, particularly for Penaeus semisulcatus and Metapenaeus monoceros, with L50 (50% retention length) values closer to their size at first maturity. The fishing efficiency indicators revealed a reduced retention probability for undersized individuals with square mesh codends. Additionally, bycatch discard rates decreased, indicating potential benefits for ecosystem conservation. This study suggests incorporating square mesh codends into fishery management regulations to enhance size selectivity and reduce bycatch during Red Sea shrimp trawling. Establishing a legal minimum landing size requirement is recommended to complement these efforts and promote sustainable fishing practices.

Development and evaluation of RFID-integrated endoscopic clips for laparoscopic surgery marking.

As advancements in surgical instruments and techniques continue to evolve, minimally invasive surgery has become increasingly preferred as a means of reducing patient pain and recovery time. However, one major challenge in performing minimally invasive surgery for early gastrointestinal cancer is accurately identifying the location of the lesion. This is particularly difficult when the lesion is confined to the lumen of the intestine and cannot be visually confirmed from the outside during surgery. In such cases, surgeons must rely on CT or endoscopic imaging to locate the lesion. However, if the lesion is difficult to identify with these images or if the surgeon has less experience, it can be challenging to determine its precise location. This can result in an excessive resection margin, deviating from the goal of minimally invasive surgery. To address this challenge, researchers have been studying the development of a marker for identifying the lesion using a radio-frequency identification (RFID) system. One proposed method for clinical application of this detection system is to attach an RFID tag to an endoscopic hemostatic clip and fix it to the intended position, providing a stable marker for the inner wall of the organ. This approach has the potential to improve the accuracy and effectiveness of minimally invasive surgery for early gastrointestinal cancer. In the development of a marker for identifying gastrointestinal lesions using a radio-frequency identification (RFID) system, the shape of the clip and suitable materials for attaching the RFID tag were determined through finite element method (FEM) analysis. A prototype of the clip was then fabricated and ex-vivo experiments were conducted using porcine intestine to evaluate the stability of the clip in relation to its position. To further evaluate the performance of the RFID-integrated clip in vivo, the clip was placed in the gastric wall of the stomach of anesthetized porcine using an endoscopic instrument. The clip was then detected using a RFID detector designed for laparoscopic approach. And later, the accuracy of detection was confirmed by incising the lesion. The design and fabrication of a clip with varying thicknesses using STS316 and STS304 stainless steel were accomplished using the results of finite element method analysis. The stability of the clip was evaluated through ex-vivo experiments, showing it to be a viable option. In-vivo experiments were performed on anesthetized porcine, in which the RFID-integrated clip was placed in the gastric wall and detected using a custom-made RFID detector. The resection margin, measured at about 30 mm from the detector position, was accomplished with low error. These findings indicate the feasibility and efficacy of using an RFID-integrated clip as a marker in minimally invasive surgery for the identification of gastrointestinal lesions. The study evaluated the feasibility of using stainless steel clips for lesion detection in endoscopic surgery using computer-aided engineering analysis and ex-vivo experimentation. Results showed that STS304 was suitable for use while STS316L was not. The ex-vivo experiments revealed that the clip holding force and tissue retention length varied depending on the location of attachment. In-vivo experiments confirmed the accuracy and usefulness of the RFID lesion detection system. However, challenges remain for its use in clinical field, such as ensuring the stability of the clip and the safe attachment of the RFID tag, which requires further research for commercialization.

High-strength carbon fiber-reinforced polyether-ether-ketone composites with longer fiber retention length manufactured via screw extrusion-based 3D printing

The mechanical properties of 3D-printed carbon fiber-reinforced polymer composites play a pivotal role in engineering applications. However, the preparation of high-performance composites through material extrusion remains a great challenge. In this study, four fiber-reinforced polyether-ether-ketone (CF/PEEK) composites with varying fiber lengths were manufactured by a homemade screw extrusion 3D printer and evaluated for their application potential. A systematic exploration was conducted on the influence of fiber length and annealing on the mechanical performance of samples. The results demonstrated that increasing fiber length and annealing enhanced the tensile and flexural strengths of components while diminishing impact strength and ductility. With an average fiber retention length of 209 μm, the annealed parts displayed exceptional tensile and flexural strengths of 169.8 MPa and 223.3 MPa, respectively, marking a 143% and 88% improvement over unannealed pure PEEK. Longer fiber retention length, higher crystallinity, and fewer internal flaws contribute to the improved mechanical performance of the samples. This study provides a broader scope for the preparation and application of 3D-printed high-performance composites.

Retention rate of subcutaneous TNF inhibitors in axial spondyloarthritis in a multicentre study from the RIC-FRANCE network

The objectives of our study were to assess retention rate, safety, and predictive factors for retention of subcutaneous (SC) TNF inhibitors (TNFi) (adalimumab (ADA), etanercept (ETN), golimumab (GOL), and certolizumab pegol (CZP)) in axial spondyloarthritis (axSpA) depending on the line of treatment in real-life conditions. A multicentre retrospective observational study was conducted including 552 patients fulfilling the ASAS criteria for axSpA followed in the RIC-France register who began SC-TNFi between 01/01/13 and 08/31/2018 for a total of 824 prescriptions. Taking all lines of treatment into account, GOL had a significantly higher retention rate compared with ADA, ETN, and CZP with a mean retention length of 59 months. As first-line bDMARDs, GOL had a significantly higher retention rate compared with ADA and ETN. ETN had the best retention rate when prescribed as at least 3rd bDMARD. Taking all lines of treatment into account, female sex, peripheral disease, BASDAI at initiation, and line of treatment were predictive factors for treatment cessation. Primary inefficiency was the most frequent reason for treatment cessation. In conclusion, GOL showed the highest retention rate in axSpA. Male sex, absence of peripheral disease, and early line of prescription were associated with better SC-TNFi retention in axSpA.

Vv-circSIZ1 mediated by pre-mRNA processing machinery contributes to salt tolerance.

CircRNAs exist widely in plants, but the regulatory mechanisms for the biogenesis and function of plant circRNAs remain largely unknown. Using extensive mutagenesis of expression plasmids and genetic transformation methods, we analyzed the biogenesis and anti-salt functions of a new grape circRNA Vv-circSIZ1. We identified Vv-circSIZ1 that is mainly expressed in the cytoplasm of xylem. CircSIZ1 is species-specific, and genomic circSIZ1-forming region of seven tested species could be backspliced in Nicotiana benthamiana, but not in Arabidopsis. The retention length of Vv-circSIZ1 flanking introns was significantly positively correlated with its generation efficiency. The precise splicing of Vv-circSIZ1 does not depend on its mature exon sequence or internal intron sequences, but on the AG/GT splicing signal sites and branch site of the flanking introns. The spliceosome activity was inversely proportional to the expression level of Vv-circSIZ1. Furthermore, RNA-binding proteins can regulate the expression of Vv-circSIZ1. The overexpression of Vv-circSIZ1 improved salt tolerance of grape and N. benthamiana. Additionally, Vv-circSIZ1 could relieve the repressive effect of VvmiR3631 on its target VvVHAc1. Vv-circSIZ1 also promoted transcription of its parental gene. Overall, these results broaden our understanding of circRNAs in plants.

Effects of the implementation of T90 extension and 52 mm square mesh codend on the bottom trawl hake fishery of the north western Mediterranean

The Spanish bottom trawl fleet operating in the Mediterranean currently uses 40 mm square mesh codends. Its selectivity is still too low to overcome the overall problem of high proportions of immature specimens in the catches. Even for some target species such as the European hake (Merluccius merluccius), there are high proportions of individuals smaller than the minimum conservation reference size (MCRS). The aim of the present work is to assess the selectivity of three different configurations of the traditional net (TRA) used in the bottom trawl hake fishery off the northwest Iberian Peninsula, each including the following modifications: i) an extension piece made of 90° turned diamond mesh (T90), ii) a 52 mm square meshed codend (52S), and iii) both modifications combined (EXP). The experimental fishing survey applied two methodologies: alternate hauls to compare the different net configurations; and the covered codend method to calculate the selectivity parameters of 52 mm square meshed codend for the main commercial species. Catch comparisons showed no discard reduction using the T90 extension piece for any of the species analysed, nor any selectivity improvement. Conversely, the 52 mm square meshed codend showed a clear discard reduction for M. merluccius and a generalized improvement of selectivity for most commercial species. This improvement raised the 50% retention length (L50) for M. merluccius to 22.2 cm, well above its MCRS (20 cm), allowing to escape 90% of the undersized individuals. However, the implementation of the 52 mm square meshed codend would involve important economic losses for main target species, like M. merluccius and Mullus barbatus, representing up to 32 and 28% of the incomes, respectively. Considering all analysed species, economic losses using the 52 mm square meshed codend would represent 27% of the incomes obtained using the current 40 mm square meshed codend in force. Despite it, transition analyses showed that the yield per recruit of the main target species would recover after two years, and even increase up to 30% and 17% for M. merluccius and M. barbatus, respectively, after the fourth year of the implementation of the 52 mm square meshed codend.

Pullout Strength of Pedicle Screws Inserted Using Three Different Techniques: A Biomechanical Study on Polyurethane Foam Block

Pullout strength is an important indicator of the performance and longevity of pedicle screws and can be heavily influenced by the screw design, the insertion technique and the quality of surrounding bone. The purpose of this study was to investigate the pullout strength of three different pedicle screws inserted using three different strategies and with two different loading conditions. Three pedicle screws with different thread designs (single-lead-thread (SLT) screw, dual-lead-thread (DLT) screw and mixed-single-lead-thread (MSLT) screw) were inserted into a pre-drilled rigid polyurethane foam block using three strategies: (A) screw inserted to a depth of 33.5 mm; (B) screw inserted to a depth of 33.5 mm and then reversed by 3.5 mm to simulate an adjustment of the tulip height of the pedicle screw and (C) screw inserted to a depth of 30 mm. After insertion, each screw type was set up with and without a cyclic load being applied to the screw head prior to the pullout test. To ensure that the normality assumption is met, we applied the Shapiro–Wilk test to all datasets before conducting the non-parametric statistical test (Kruskal–Wallis test combined with pairwise Mann–Whitney-U tests). All screw types inserted using strategy A had a significantly greater pullout strength than those inserted using strategies B and C, regardless of if the screw was pre-loaded with a cyclic load prior to testing. Without the use of the cyclic pre-load, the MSLT screw had a greater pullout strength than the SLT and DLT screws for all three insertion strategies. However, the fixation strength of all screws was reduced when pre-loaded before testing, with the MSLT screw inserted using strategy B producing a significantly lower pullout strength than all other groups (p < 0.05). In contrast, the MSLT screw using insertion strategies A and C had a greater pullout strength than the SLT and DLT screws both with and without pre-loading. In conclusion, the MSLT pedicle screw exhibited the greatest pullout strength of the screws tested under all insertion strategies and loading conditions, except for insertion strategy B with a cyclic pre-load. While all screw types showed a reduced pullout strength when using insertion strategy B (screw-out depth adjustment), the MSLT screw had the largest reduction in pullout strength when using a pre-load before testing. Based on these findings, during the initial screw insertion, it is recommended to not fully insert the screw thread into the bone and to leave a retention length for depth adjustment to avoid the need for screw-out adjustment, as with insertion strategy B.

Standardized catch per unit effort and size compositions of Atlantic bonito, Sarda sarda (Bloch, 1793), harvested by artisanal fisheries in the Senegalese Exclusive Economic Zone (SEEZ)

Atlantic bonito, Sarda sarda (Bloch, 1793), is a valuable small tuna species to coastal countries and local communities. This species is heavily exploited by artisanal fisheries in the Senegalese Exclusive Economic Zone (SEEZ). The common gears used in artisanal fisheries for catching Atlantic bonito are gillnets, purse seines, longlines, and sleeping nets. Although catches of this species have increased in recent years, little is known about the Atlantic bonito catch per unit effort (CPUE) and size selectivity in theregion. As this information is relevant for many stock assessments, available catch, effort and size data from Atlantic bonito harvested over 15 years (2004–2018) with different gears were used in the present study to calculate the nominal and standardized CPUE, size-frequency distribution and length at retentions (50 % and 95 % selectivity) of the species. To eliminate the effects of temporal, spatial, and environmental factors, the Atlantic bonito CPUE was standardized using generalized linear and additive models. The retention length at 50 % and 95 % for each year and gear was calculated from the cumulative length frequency distribution as a proxy for selectivity. Optimal model standardization CPUE results showed a significant trend for gillnets, ranging from 4.6 kg/trip in 2005–92.65 kg/trip in 2018, while sleeping nets showed lower CPUE values, ranging from 2.12 kg/trip in 2004 up to 0.83 kg/trip in 2018. This study showed that the year, month, and fishing Area variables were the main factors affecting the nominal CPUE for all scenarios evaluated in this study. Catch data, CPUE and selectivity results have shown that gillnets are the most selective and efficient among the four main gears used to catch Atlantic bonito in the SEEZ.

Effect of codend mesh sizes on the size selectivity and exploitation pattern of cocktail shrimp (Trachypenaeus curvirostris) in shrimp trawl fishery of the South China Sea

This study aims at improving fishery management by testing and comparing the size selectivity and exploitation pattern of diamond-mesh codends, with mesh sizes ranging from 25 to 54 mm, for cocktail shrimp (Trachypenaeus curvirostris) in the South China Sea (SCS). Beginning from 25 mm, the minimum mesh size regulated by the shrimp trawl fishery industry, we investigated how the mesh sizes of the codends would affect the size selectivity and exploitation pattern in reference to the minimum conservation reference size (MCRS, 7.0 cm total length) of cocktail shrimp in the SCS. According to our results, the selective properties of the codend mesh sized at 25 mm in line with the regulation failed to protect the undersized individuals of cocktail shrimp because of its 50% retention length of 5.85 cm (confidence interval, CI: 5.16–6.18 cm), far less than the MCRS of cocktail shrimp. As the retention probability of a shrimp with a MCRS length was as high as 97.45 % (CI: 86.86–100.00%), more than 40% of the undersized shrimp was retained. It was proved that increasing the codend mesh size did not significantly improve the size selectivity and exploitation pattern which might be improved by other gear modifications.

Design a Robot System for Tomato Picking Based on YOLO v5

Tomato picking robots can save labor and improve production efficiency, which is of great significance for facility tomato planting. The picking mode of the Tomato Picking Robot has an important impact on fruit picking quality and efficiency. At present, in the process of fruit picking, the rough recognition of fruit positioning needs compensation accuracy. The picking mode is usually to capture the fruit in a large range and then separate the fruit peduncles in a specific position. In the process of grasping and pulling the fruit, it may cause damage to the fruit and plant, which will reduce the fruit quality. Moreover, The retention length of peduncles is also difficult to control, resulting in difficulties in transportation and storage. Therefore, the prediction, location and segmentation of separation points on tomato images are an important guarantee for efficient and lossless harvest. In this study considering the changeable conditions such as light change and branches and leaves interference, YOLO V5 is used to confirm the position relationship between tomatoes and peduncles. The region of interest for peduncles picking is reduced according to the growth characteristics of the fruit. Then, taking the boundary boxes center of the peduncles as the picking points, the corresponding depth information is obtained and the robot is controlled to complete the picking task. The experimental results show that this method can recognize and locate tomato picking points under complex near-color backgrounds. The average recognition time of a single frame image is 104 ms, which meets the real-time requirements of automatic picking. Compared with the SSD algorithm, it has obvious advantages.

Comparing size selectivity and exploitation pattern of diamond-mesh codends for Southern velvet shrimp (Metapenaeopsis palmensis) in shrimp trawl fishery of the South China Sea.

In this study, size selectivity and exploitation pattern of six diamond-mesh codends with different mesh sizes, ranging from 25 to 54 mm, for Southern velvet shrimp (Metapenaeopsis palmensis) were tested and compared in a shrimp trawl fishery of the South China Sea (SCS). We used a codend with a mesh size of 25 mm (D25) as a starting point, which is the minimum mesh size (MMS) currently regulated in the studied area. Four different fishing population scenarios were applied to quantify and compare how mesh sizes of codends used would impact the size selectivity and exploitation pattern for the target shrimp species. The results demonstrated that the D25 codend was not proper for protecting juvenile shrimp at the studied area. By applying this legal codend, L50 (50% retention length) of the target shrimp species was below its minimum conservation reference size (MCRS, 7.0 cm total length), the retention probability of shrimp with a length of MCRS was above 95% CI [91–99] and more than 43% of undersized shrimp was retained. To mitigate the bycatch issue of undersized shrimp, increasing the mesh size in the diamond mesh codend is a simple and effective option. However, the loss of catch efficiency for marketable shrimp is a major concern while increasing the mesh size. A good compromise between releasing undersized shrimp and maintaining the legal individuals is manifested by using the codend with 35 mm mesh size (D35). Our study will be beneficial for the management of shrimp trawl fisheries in the SCS.

Size selection and exploitation pattern of diamond mesh codends with different mesh sizes in demersal trawl fishery for banded scad (Caranx (Atule) kalla) in the South China Sea

Size selection and exploitation pattern of diamond-mesh codends with different mesh sizes, 25 to 54 mm, for demersal trawl fishery targeting banded scad (Caranx (Atule) kalla) was tested and compared using the covered codend method in the South China Sea. Our results demonstrated that the selective parameters, L50 (50% retention length) and SR (selection range), would increase as the mesh sizes of codends increased, and the confidence intervals in these parameters became relatively wider when the mesh sizes increasing to 40 mm. The results of exploitation pattern showed that catch efficiency of codends would decrease when the mesh sizes increased. Considering compromise of protecting juvenile fish and the profitability of fishermen, the codend with 30 mm mesh size would be the best choice to target banded scad among all tested codends. Our study will be beneficial to the fishery management in the studied area.

Design of a vane mixer with controlled extensional/shear strength ratio and its application for carbon fiber/polyamide 6 composites

AbstractIn this work, a novel melt mixing method and its corresponding mixing device are developed. The extensional/shear strength ratio of the device can be controlled by adjusting its eccentricity. The structure and working principle of the device are introduced in detail. Carbon fiber (CF)/polyamide 6 (PA6) composites are prepared via this novel mixing device. The influences of eccentricity and mixing time on the morphology, CF length, thermal, mechanical, and electrical properties of CF/PA6 composites are studied. Scanning electron microscopy results show that CFs uniformly disperse in the matrix and interfacial adhesion between CFs and PA6 is improved. It is observed that CF length and its distributions can be optimized by changing eccentricity. The maximum average fiber length is about 351 μm. Differential scanning calorimetry results exhibit that the Xc increases 6.5% when eccentricity is 2 mm. Mechanical test results show tensile strength and modulus increase first and then decrease with the increasing eccentricities or mixing time. Electrical property measurement shows an obvious increase when eccentricity is 2 mm due to good fiber dispersion and long fiber retention length. The experimental results indicate that the novel mixing method and its corresponding apparatus provide an environment‐friendly and effective way to prepare polymer‐based composites.

Effect of series explosion effects on the fiber length, fiber dispersion and structure properties in glass fiber reinforced polyamide 66

Nowadays, glass fiber (GF) reinforced polyamide 66 (PA66) composites have attracted strong interests in commercial and engineering applications due to many advantages, such as corrosion resistance, high potential of integration, self‐lubricating, and high toughness. However, it is very difficult for traditional plastic molding equipment to concurrently obtain the increase of fiber retention length and the improvement of fiber dispersion during the PA66/GF composites manufacturing, which greatly limit the widespread application of such composites. An innovative twin eccentric rotor volume pulsating plasticizing transportation equipment (TERE) based on series explosion effects, is applied to prepare PA66/GF composites at different rotor speeds and fiber loadings. Inside the PA66/GF30 composite prepared by TERE, the fibers are evenly dispersed in polymer matrix and the average fiber length increases by 3.2 times when compared to that of twin‐screw plasticizing transportation equipment (TSE). The Charpy impact strength of PA66/GF composites prepared by TERE is nearly twice that of TSE at all fiber contents. The fatigue properties, thermal oxygen aging properties, and creep properties of the TERE composites exhibit better effects than the TSE composites, indicating that the TERE can ensure longer fiber length and better dispersion effect simultaneously.

A meta-analysis of plaice size-selection data in otter trawl codends

The influence that mesh size, the number of open meshes around the circumference, twine thickness and catch size have on the size-selection of plaice (Pleuronectes platessa) in otter trawl codends is investigated by synthesising the data from 164 hauls using 25 gear configurations during 9 trips.All these variables have an effect on selection. The 50 % retention length (L50) increases by 1.9 cm for every 10 mm increase of mesh size and decreases by 0.24 cm for every doubling of catch. The selection range decreases by 3.8 % for each increase of 10 open meshes and increases by 12.3 % for each 1 mm increase of twine thickness. The mesh size and twine thickness effects have strong support from the data. The open meshes and catch size effects have less support and should be treated with some caution.There is good correspondence between the predictions of the analysis presented here and the L50 estimates of beam trawl codend selectivity trials, which is noteworthy given the many operational differences between the two fishing methods.

Selectivity of Two Commercial Dredges Fished in the Northwest Atlantic Sea Scallop Fishery

Size selectivity curves were estimated for two commercial dredge configurations used in the United States Atlantic sea scallop (Placopecten magellanicus) fishery. Traditionally, the New Bedford Style dredge (New Bedford dredge) has been used by the commercial fleet; however, since 2013, the Coonamessett Farm Turtle Deflector Dredge (turtle dredge) has been required seasonally in the Mid-Atlantic region to minimize the capture of sea turtles. This analysis provides estimates of selectivity and relative efficiency for the turtle dredge and the New Bedford dredge. Selectivity information for the turtle dredge is currently unknown, and selectivity for the New Bedford dredge was originally assessed in 2008. The Share Each Lengths Catch Total method was used to model scallop catch-at-length data for each commercial dredge with data collected during the Virginia Institute of Marine Science fishery-independent surveys in 2015 to 2017, conducted onboard commercial fishing vessels. The surveys were conducted in the Mid-Atlantic and Georges Bank regions of the resource in three distinct areas. A paired study design was used, where a nonselective National Marine Fisheries Service sea scallop survey dredge and either the turtle dredge or New Bedford dredge were towed simultaneously at each survey station. To assess for time-varying changes in selectivity, results were compared with the 2008 New Bedford dredge analysis. Results indicated the 50% retention length was 98.2 mm, with a selection range of 28.2 mm and a relative efficiency of 0.83 for the turtle dredge. New Bedford dredge results estimated a 50% retention length of 107.4 mm, selection range of 50.5 mm and relative efficiency of 0.81. Comparing selectivity profiles for the turtle dredge and New Bedford dredge with the 2008 results indicated a shift toward increased retention probability for smaller size classes of scallops.

Reducing discards of demersal species using a 100 mm square mesh cylinder: Size selectivity and catch comparison analysis

We assessed the impact of an additional 100 mm square mesh cylinder (SMC) on the selective property of the demersal whitefish trawl in the Celtic Sea. Sea trials were conducted on board a French trawler using twin trawl rigging. We tested the effects of the position of the SMC (in front of and behind the mandatory 100 mm square mesh panel) and of the insertion of a dispersive float. Selectivity analysis revealed the 50% retention length (L50) to be greater than the Minimum Conservation Reference Sizes regardless of species (haddock, whiting or megrim) or rigging configuration. Results did not reveal a clear effect of the SMC position. However, the insertion of the float led to a decrease in selection ranges suggesting enhanced contact probabilities with the square meshes. With the largest L50 values, the SMC placed in the front position (and without the float) proved to be the most selective rigging configuration and was then tested under commercial conditions. Catch comparisons revealed that the test gear retained less fish across all size classes than the commercial gear. For haddock, the test gear retained less fish below 50 cm in length. Catch comparisons also indicated significant discards of fish above the MCRS, i.e. “high-grading” practices. Under the requirements of the landing obligation (LO), unwanted catches must be stored on-board and landed regardless of economic value. The SMC is thus a valuable tool to mitigate the impact of the LO on the demersal whitefish fishing fleets operating in the Celtic Sea.

1277. Retention Among Adolescents with Mental Health Diagnoses on Pre-Exposure Prophylaxis (RAMP) Study

BackgroundThe CDC reported in 2017 that 21% of new HIV diagnoses were composed of persons 13–24 years old. New York State (NYS) is addressing this with the Ending the Epidemic initiative, started in 2014, which emphasized pre-exposure prophylaxis (PrEP) for persons at risk of acquiring HIV. Though PrEP can effectively prevent HIV transmission, NYS minors were only granted capacity to accept PrEP in 2017. The Adolescent Medicine Trials Network found clinicians had varying perceptions on whether mental health diagnoses (MHD) were a barrier to adolescent PrEP utilization. This study aims to test the hypothesis that patients with MHD do not differ in PrEP retention length when compared with adolescents without MHD.MethodsThis is a retrospective single-center study analyzing self-reported visit data for adolescent enrolled on PrEP (n = 27) in the Capital District, NY. MHD were confirmed with clinician notes and retention to PrEP was defined as attending appointments. Between-group differences were compared using Fisher’s Exact Test (FET). Kaplan–Meier curves were compared using the log-rank test.ResultsOf the 27 adolescents enrolled on PrEP between Sep 2015-March 2019, most self-identified as males (93%), MSM (85%), white (74%), and 13 (48%) had a MH diagnosis. Anxiety was the most common MHD (69%), followed by depression (38%). The mean age was 20.3 years (16–24). The average PrEP retention for patients with and without MHD were 262±136 and 292±138 days, respectively (P = 0.575). For patients with MHD, follow-up at 1-month, 3-months and 1-year was 10 (77%), 8 (62%), and 5 (39%), respectively. For patients without MHD, follow-up at 1-month, 3-months, and 1-year was 11 (79%), 10 (71%), 5 (36%), respectively. Follow-up between adolescents with and without MHD was compared at 1-month (P = 0.086, FET), 3-months (P = 0.695, FET), and 1-year (P = 1.0, FET). Adolescents’ retention on PrEP was depicted on Kaplan–Meier curves (Figure 1). Log-rank test indicated that PrEP retention is not significantly associated with MHD (χ2(1) = 0.1, P = 0.727).ConclusionAdolescents with and without MHD did not significantly differ in PrEP retention outcomes. The RAMP study elucidates a potentially incorrect provider bias regarding PrEP retention and MHD. Future investigation should be done prospectively with larger sample size. Disclosures All authors: No reported disclosures.

Effect of continuous elongational flow on structure and properties of short glass fiber reinforced polyamide 6 composites

Abstract Short glass fiber (SGF) reinforced polyamide 6 (PA6) composite is an important thermoplastic engineering plastic with excellent properties such as high toughness, high strength, self-lubrication and corrosion resistance. However, due to the characteristics of difficult to disperse and easy to break of the fibers during processing, the application range of the PA6/SGF composite is limited. An innovative twin-eccentric rotor extruder (TERE), which can generate continuous elongation flow, is applied to fabricate the PA6/SGF composites in different fiber content and rotor speed. The fiber length remains good and the fibers are well dispersed in the polymer matrix so that the residual fibers after burn-off form a network interlock structure. That is, the TERE based on continuous elongational flow not only disperses the glass fibers effectively, but also reduces the fiber breakage. Under the action of elongation flow field, the fiber agglomerates undergo a periodic convergence-divergience effect, which forces the fiber agglomerates to separate from each other and disperse homogeneously in the polymer matrix. Interestingly, the charpy impact strength of the composites prepared by the TERE is about double that prepared by the twin-screw extruder (TSE) at each fiber content, which can be attributed to the more efficient fiber dispersion and longer fiber retention length. The thermal oxygen aging property, fatigue property, and creep property analysis also indicate that the TERE has a better dispersion effect than the TSE, and the fibers retain a longer length in the PA6 matrix, thereby providing more excellent service properties.