Investigation of DC-8 nacelle modifications to reduce fan-compressor noise in airport communities. Part 3 - Static tests of noise suppressor configurations, May 1967 - October 1969

Static tests of noise suppressor configurations of DC-8 aircraft nacelle modifications to reduce fan-compressor noise levels - Part

An acoustical study of the KIWI B nuclear rocket

Kiwi B nuclear rocket acoustics - sound pressure distribution, energy conversion, and power distributio

Reverse engineering forces responsible for dynamic clustering and spreading of multiple nuclei in developing muscle cells

How cells position organelles is a fundamental biological question. During Drosophila embryonic muscle development, multiple nuclei transition from being clustered together, to splitting into two smaller clusters, to spreading along the myotube's length. Perturbations of microtubules and motor proteins disrupt this sequence of events. These perturbations do not allow intuiting which molecular forces govern the nuclear positioning; we therefore used computational screening to reverse engineer and identify these forces. The screen reveals three models: two suggest that the initial clustering is due to the nuclear repulsion from the cell poles, while the third, most robust, model poses that this clustering is due to a short-ranged internuclear attraction. All three models suggest that the nuclear spreading is due to the long-ranged internuclear repulsion. We test the robust model quantitatively by comparing it to data from perturbed muscle cells. We also test the model by using agent-based simulations with elastic dynamic microtubules and molecular motors. The model predicts that, in longer mammalian myotubes with a great number of nuclei, the spreading stage would be preceded with segregation of the nuclei into a large number of clusters, proportional to the myotube length, with a small average number of nuclei per cluster

Multiple C-Terminal Tails within a Single \u3cem\u3eE. coli\u3c/em\u3e SSB Homotetramer Coordinate DNA Replication and Repair

Escherichia coli single-stranded DNA binding protein (SSB) plays essential roles in DNA replication, recombination and repair. SSB functions as a homotetramer with each subunit possessing a DNA binding domain (OB-fold) and an intrinsically disordered C-terminus, of which the last nine amino acids provide the site for interaction with at least a dozen other proteins that function in DNA metabolism. To examine how many C-termini are needed for SSB function, we engineered covalently linked forms of SSB that possess only one or two C-termini within a four-OB-fold “tetramer”. Whereas E. coli expressing SSB with only two tails can survive, expression of a single-tailed SSB is dominant lethal. E. coli expressing only the two-tailed SSB recovers faster from exposure to DNA damaging agents but accumulates more mutations. A single-tailed SSB shows defects in coupled leading and lagging strand DNA replication and does not support replication restart in vitro. These deficiencies in vitro provide a plausible explanation for the lethality observed in vivo. These results indicate that a single SSB tetramer must interact simultaneously with multiple protein partners during some essential roles in genome maintenance

Maximum Likelihood Estimation of Head Motion Using Epipolar Consistency

Open gantry C-arm systems that are placed within the interventional room enable 3-D imaging and guidance for stroke therapy without patient transfer. This can profit in drastically reduced time-totherapy, however, due to the interventional setting, the data acquisition is comparatively slow. Thus, involuntary patient motion needs to be estimated and compensated to achieve high image quality. Patient motion results in a misalignment of the geometry and the acquired image data. Consistency measures can be used to restore the correct mapping to compensate the motion. They describe constraints on an idealized imaging process which makes them also sensitive to beam hardening, scatter, truncation or overexposure. We propose a probabilistic approach based on the Student’s t-distribution to model image artifacts that affect the consistency measure without sourcing from motion

Effect of the Predecessor and the Nitrogen Rate on Productivity and Essential Oil Content of Coriander (Coriandrum sativum L.) in Southeast Bulgaria

Received: May 31st, 2022 ; Accepted: August 13th, 2022 ; Published: September 19th, 2022 ; Correspondence: [email protected] (Coriandrum sativum L.) is one of the most important essential oil crops on a global scale. Coriander productivity is determined by the genotype, the environmental factors, as well the agronomic practices. A field experiment was conducted in Southeast Bulgaria during three vegetation seasons (2015, 2016, and 2017). The present study aimed at analysing the influence of two crop predecessors (winter wheat and sunflower) and four nitrogen (N) levels (0, 40, 80, and 120 kg ha-1 ). Productivity elements, seed yield, and seed essential oil content of coriander (cv. Mesten drebnoploden) were under evaluation. The results obtained showed that winter wheat was a more suitable predecessor of coriander in comparison to sunflower. The highest results regarding the number of umbels per plant, the umbel’s diameter, the number of umbellets per umbel, the number of seeds per umbel, the seed weight per plant, the 1,000 seed mass, as well as the seed yield for the rate of 80 kg ha-1 of N were recorded. The highest essential oil content after applying 120 kg ha-1 of N was established. Increasing the N level from 0 to 120 kg ha-1 led to a positive and significant effect on essential oil yield. No significant differences between the N rates of 80 and 120 kg ha-1 were recorded. The received results contributed for the evaluatation of the optimum nitrogen level, as well as for the determination of a more suitable predecessor of coriander in order to obtain the highest yield of better quality in the region of Southeast Bulgaria

Design and Manufacture of a Highly Reliable, Miniaturized and Low Mass Shutter Mechanism

This paper describes the development, manufacturing and testing of a lightweight shutter mechanism made of titanium for the MERTIS Instrument. MERTIS is a thermal infrared imaging spectrometer onboard ESA's future BepiColombo mission to Mercury. The mechanism is built as a parallelogram arrangement of flexible hinges, actuated by a voice coil. In a first test run, it was shown that the selected EDM processing led to the generation of titanium oxides and an oxygen-enriched surface layer on the substrate (so called alpha-case layer). In the revised version of the shutter, it was possible to manufacture the complex geometry by micro-milling and an adjacent pickling procedure. The adequacy of this approach was verified by lifetime and vibration testing

Additive Equivalence in Turbulent Drag Reduction by Flexible and Rodlike Polymers

We address the "Additive Equivalence" discovered by Virk and coworkers: drag reduction affected by flexible and rigid rodlike polymers added to turbulent wall-bounded flows is limited from above by a very similar Maximum Drag Reduction (MDR) asymptote. Considering the equations of motion of rodlike polymers in wall-bounded turbulent ensembles, we show that although the microscopic mechanism of attaining the MDR is very different, the macroscopic theory is isomorphic, rationalizing the interesting experimental observations.Comment: 8 pages, PRE, submitte

Stress‐response balance drives the evolution of a network module and its host genome

Stress response genes and their regulators form networks that underlie drug resistance. These networks often have an inherent tradeoff: their expression is costly in the absence of stress, but beneficial in stress. They can quickly emerge in the genomes of infectious microbes and cancer cells, protecting them from treatment. Yet, the evolution of stress resistance networks is not well understood. Here, we use a two‐component synthetic gene circuit integrated into the budding yeast genome to model experimentally the adaptation of a stress response module and its host genome in three different scenarios. In agreement with computational predictions, we find that: (i) intra‐module mutations target and eliminate the module if it confers only cost without any benefit to the cell; (ii) intra‐ and extra‐module mutations jointly activate the module if it is potentially beneficial and confers no cost; and (iii) a few specific mutations repeatedly fine‐tune the module's noisy response if it has excessive costs and/or insufficient benefits. Overall, these findings reveal how the timing and mechanisms of stress response network evolution depend on the environment

Impact Of Redesigning A Large-Lecture Introductory Earth Science Course To Increase Student Achievement And Streamline Faculty Workload

A Geological Perspective is a general education survey course for non-science majors at a large southwestern research extensive university.  The class has traditionally served 600 students per semester in four 150-student lectures taught by faculty, and accompanied by optional weekly study groups run by graduate teaching assistants.  We radically redesigned the course to 1) improve student learning and, simultaneously, 2) reduce faculty effort.   Previously optional study groups were replaced by weekly mandatory break-out sessions, run largely by undergraduate peer mentors.  Twice weekly, lectures are brief with a large portion of class time allocated to active learning in small groups.  Completing quizzes on-line reduced grading and allowed students more flexibility.  Evaluation of the redesign (mixed methods, quasi-experimental, two-group, pre-test-post-test, multiple-measures study design) revealed no significant improvements in learner outcomes insofar as the instruments could measure. However, qualitative results reveal that overall students greatly valued their learning experience under the redesign.  In addition, the redesign reduced the departmental cost of the class offering per student by more than half.