Search

Undergraduate students participating in the UCLA Undergraduate Research Consortium for Functional Genomics (URCFG) have conducted a two-phased screen using RNA interference (RNAi) in combination with fluorescent reporter proteins to identify genes important for hematopoiesis in Drosophila. This screen disrupted the function of approximately 3500 genes and identified 137 candidate genes for which loss of function leads to observable changes in the hematopoietic development. Targeting RNAi to maturing, progenitor, and regulatory cell types identified key subsets that either limit or promote blood cell maturation. Bioinformatic analysis reveals gene enrichment in several previously uncharacterized areas, including RNA processing and export and vesicular trafficking. Lastly, the participation of students in this course-based undergraduate research experience (CURE) correlated with increased learning gains across several areas, as well as increased STEM retention, indicating that authentic, student-driven research in the form of a CURE represents an impactful and enriching pedagogical approach.

This paper presents the results of a field load test program used to investigate group effects on the pullout capacity of single-helix 'deep' helical piles/anchors in sand. The high tensile capacity and silent installation of helical piles has given them serious consideration as an alternative to conventional deep foundations and anchors for offshore renewable energy structures. New offshore applications may consider the use of groups of helical piles to resist structural loads. Group interaction effects are known to occur in helical piles, but there is a scarcity of field data on groups in sands under tensile loading. This study involved the installation and load testing of single-helix 152 mm diameter round shaft piles and pile groups embedded in sand to depths of 12 and 18 helix diameters below the ground surface. The study was designed to explore the effects of close pile spacing, group configuration (i.e., number of piles), and soil strength (i.e., friction angle) as interpreted from cone penetration test (CPT) resistance. The results showed group efficiencies ranging from about 0.6 to 1.0 at a horizontal spacing of 2 to 3 times the helix diameter in sands with friction angles of about 39[degrees] to 44[degrees]. The data from this study may also be useful for validation of numerical models for analysis of helical pile group interactions. Key words: helical piles, screw piles, helical anchors, pile groups, group efficiency, renewable energy, offshore wind. Cet article presente les resultats d'un programme d'essai de charge sur le terrain utilise pour etudier les effets de groupe sur la capacite d'arrachement des pieux/ancres helicoidaux << profonds >> a une seule helice dans le sable. La capacite de traction elevee et l'installation silencieuse des pieux helicoidaux ont permis de les considerer serieusement comme une alternative aux fondations profondes et aux ancrages conventionnels pour les structures d'energie renouvelable en mer. Les nouvelles applications offshore peuvent envisager l'utilisation de groupes de pieux helicoidaux pour resister aux charges structurelles. Les effets d'interaction de groupe sont connus pour se produire dans les pieux helicoidaux, mais il y a peu de donnees de terrain sur les groupes dans les sables sous charge de traction. Cette etude a consiste a installer et a tester la charge de pieux ronds a une seule helice de 152 mm de diametre et de groupes de pieux enfonces dans le sable a des profondeurs de 12 et 18 diametres d'helice sous la surface du sol. L'etude a ete concue pour explorer les effets de l'espacement etroit des pieux, de la configuration du groupe (c.-a-d. le nombre de pieux) et de la resistance du sol telle (c.-a-d. l'angle de frottement) qu'interpretee a partir de l'essai de penetration au cone (CPT). Les resultats ont montre des efficacites de groupe allant d'environ 0,6 a 1,0 a un espacement horizontal de 2 a 3 fois le diametre de l'helice dans des sables avec des angles de friction d'environ 39[degrees] a 44[degrees]. Les donnees de cette etude peuvent egalement etre utiles pour la validation de modeles numeriques pour l'analyse des interactions des groupes de pieux helicoidaux. [Traduit par la Redaction] Mots-cles : pieux helicoidaux, pieux visses, ancrages helicoidaux, groupes de pieux, efficacite des groupes, energie renouvelable, eolien offshore., Introduction Long after Alexander Mitchell proposed helical piles (or screw piles) for use as marine foundations and moorings in the 1840s (Lutenegger 2011), there is renewed interest in using them [...]

Ventricular fibrillation is a common life-threatening arrhythmia. The ECG of VF appears chaotic but may allow identification of sustaining mechanisms to guide therapy.We hypothesized that rotors and focal sources manifest distinct features on the ECG, and computational modeling may identify mechanisms of such features.VF induction was attempted in 31 patients referred for ventricular arrhythmia ablation. Simultaneous surface ECG and intracardiac electrograms were recorded using biventricular basket catheters. Endocardial phase maps were used to mechanistically classify each VF cycle as rotor or focally driven. ECGs were analyzed from patients demonstrating both mechanisms in the primary analysis and from all patients with induced VF in the secondary analysis. The ECG voltage variation during each mechanism was compared. Biventricular computer simulations of VF driven by focal sources or rotors were created and resulting ECGs of each VF mechanism were compared.Rotor-based VF exhibited greater voltage variation than focal source-based VF in both the primary analysis (n = 8, 110 ± 24% vs. 55 ± 32%, P = 0.02) and the secondary analysis (n = 18, 103 ± 30% vs. 67 ± 34%, P = 0.009). Computational VF simulations also revealed greater voltage variation in rotors compared to focal sources (110 ± 19% vs. 33 ± 16%, P = 0.001), and demonstrated that this variation was due to wavebreak, secondary rotor initiation, and rotor meander.Clinical and computational studies reveal that quantitative criteria of ECG voltage variation differ significantly between VF-sustaining rotors and focal sources, and provide insight into the mechanisms of such variation. Future studies should prospectively evaluate if these criteria can separate clinical VF mechanisms and guide therapy.

This paper presents a study on the hysteretic damping of cyclic axially loaded piles in sand that would be of particular interest to the design and analysis of offshore wind turbine (OWT) jacket structures. Foundation damping can help to reduce fatigue loads thereby leading to leaner designs and/or extended design life. Damping has been studied in laterally loaded OWT monopiles, but there is little information and guidance for estimating damping for axially loaded piles in an OWT jacket structure. The objective of this study was to (1) document hysteretic damping in axially loaded pipe piles in sands and (2) develop a simple and practical numerical approach for predicting the hysteretic damping (and stiffness) properties for dynamic numerical analysis of the OWT structure. First, existing low-frequency pile load test data are compiled from the literature and analyzed to evaluate the hysteretic damping. Second, a simple quasi-static equivalent linear modeling approach is described that can be used to predict hysteretic damping at the pile head using a conventional static t-z analysis. The axial stiffness and damping ratios predicted for the test piles at the pile head compared very well to the observed pile data when the maximum interface friction was accurately predicted. [ABSTRACT FROM AUTHOR]

Plate and screw anchors provide a significant uplift capacity and have multiple applications in both onshore and offshore geotechnical engineering. Uplift design methods are mostly based on semi-empirical approaches assuming a failure mechanism, a normal and a shear stress distribution at failure and empirical factors back-calculated against experimental data. However, these design methods are shown to under- or overpredict most of the existing larger scale experimental tests. Numerical FE simulations are undertaken to provide new insight into the failure mechanism and stress distribution which should be considered in anchor design in dense sand. Results show that a conical shallow wedge whose inclination to the vertical direction is equal to the dilation angle is a good approximation of the failure mechanism in sand. This shallow mechanism has been observed in each case for relative embedment ratios (depth/diameter) ranging from 1 to 9. However, the stress distribution varies non-linearly with depth, due to the soil deformability and progressive failure. A sharp peak of normal and shear stress can be identified close to the anchor edge, before a gradual decrease with increasing distance along the shear plane. The peak stress magnitude increases almost linearly with embedment depth at larger relative embedment ratios. Although further research is necessary, these results lay the basis for the development of a new generation of design criteria for determining anchor capacity at the ultimate limiting state.

Background: Men with Klinefelter Syndrome develop some degree of seminiferous tubule degeneration, hyalinization, and fibrosis by adulthood. However, the pathophysiology surrounding testicular fibrosis in Klinefelter Syndrome patients remains incompletely understood. Objectives: To perform a systematic review of literature studying the mechanisms of fibrosis initiation or propagation in Klinefelter Syndrome testes. Materials/methods: PubMed was searched systematically for articles specific to Klinefelter Syndrome and the process of fibrosis. Articles that did not contain original data or specifically addressed the target material were excluded. Additional references were extracted when pertinent from the reference lists of included studies. Results: Primary search yielded 139 articles for abstract review, which was narrowed to 16 for full‐text review. Following full‐text review, eight contained original data and met topic criteria, with one paper added from reference review for a total of nine papers. Discussion: The date range for included papers was 1992–2022. The proposed mechanisms of fibrosis mainly were centered around the impact of altered Sertoli cells on germ cells, the hormonal impact on Leydig cells, the inflammation mediated by mast cells, or the fibrous extracellular matrix deposition by peritubular myoid cells. Additionally, discussions of the role of the altered microvasculature and the specific proteins involved in the blood‐testis barrier or the seminiferous tubule architecture are reviewed. Recent papers have incorporated advanced sequencing and offer future directions for targeted gene expression analysis. Still, much of the published data consists solely of immunohistological assessment by age range, creating difficulties in extrapolating causality. Conclusion: The specific initiating factors of fibrosis of the seminiferous tubules and the propagation mechanisms unique to Klinefelter Syndrome remain incompletely understood with a relative paucity of data. Nonetheless, academic interest is increasing in this field as it may further elucidate the pathophysiology behind Klinefelter syndrome. [ABSTRACT FROM AUTHOR]

As an alternative to a field-based liquefaction resistance approach, cyclic triaxial tests with bender elements were used to develop a new correlation between cyclic resistance ratio (CRR) and overburden stress-corrected shear-wave velocity ([V.sub.S1]) for two nonplastic silts obtained from Providence, Rhode Island. Samples of natural nonplastic silt were recovered by block sampling and from geotechnical borings/split-spoon sampling. The data show that the correlation is independent of the soils' stress history as well as the method used to prepare the silt for cyclic testing. The laboratory results indicate that using the existing field-based CRR-[V.sub.S1] correlations will significantly overestimate the cyclic resistance of the Providence silts. The strong dependency of the CRR-[V.sub.S1] curves on soil type also suggests the necessity of developing silt-specific liquefaction resistance curves from laboratory cyclic tests performed on reconstituted samples. DOI: 10.1061/(ASCE)1090-0241(2008)134:1(37) CE Database subject headings: Silts; Liquefaction; Cyclic tests; Shear waves; Velocity.