Dynamic characteristics of single crystal SSME blades

The Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) blades are currently manufactured using a directionally solidified (DS) material, MAR-M-246+Hf. However, a necessity to reduce the occurrence of fatigue cracking within the DS blades has lead to an interest in the use of a single crystal (SC) material, PWA-1480. A study was initiated to determine the dynamic characteristics of the HPFTP blades made of SC material and find possible critical engine order excitations. This study examined both the first and second stage drive turbine blades of the HPFTP. The dynamic characterization was done analytically as well as experimentally. The analytical study examined the SC first stage HPFTP blade dynamic characteristics under typical operating conditions. The blades were analyzed using MSC/NASTRAN and a finite element model. Two operating conditions, 27500 RPM and 35000 RPM, were investigated

Stage-Specific Timing of the microRNA Regulation of \u3cem\u3elin-28\u3c/em\u3e by the Heterochronic Gene \u3cem\u3elin-14\u3c/em\u3e in \u3cem\u3eCaenorhabditis elegans\u3c/em\u3e

In normal development, the order and synchrony of diverse developmental events must be explicitly controlled. In the nematode Caenorhabditis elegans, the timing of larval events is regulated by hierarchy of proteins and microRNAs (miRNAs) known as the heterochronic pathway. These regulators are organized in feedforward and feedback interactions to form a robust mechanism for specifying the timing and execution of cell fates at successive stages. One member of this pathway is the RNA binding protein LIN-28, which promotes pluripotency and cell fate decisions in successive stages. Two genetic circuits control LIN-28 abundance: it is negatively regulated by the miRNA lin-4, and positively regulated by the transcription factor LIN-14 through a mechanism that was previously unknown. In this report, we used animals that lack lin-4 to elucidate LIN-14’s activity in this circuit. We demonstrate that three let-7 family miRNAs—miR-48, miR-84, and miR-241—inhibit lin-28 expression. Furthermore, we show genetically that these miRNAs act between lin-14 and lin-28, and that they comprise the pathway by which lin-14 positively regulates lin-28. We also show that the lin-4 family member mir-237, also regulates early cell fates. Finally, we show that the expression of these miRNAs is directly inhibited by lin-14 activity, making them the first known targets of lin-14 that act in the heterochronic pathway

Electrical Treeing in Silicone Rubber

Electrical treeing has been widely studied in a range of polymeric materials. In these investigations, the morphology and PD patterns associated with the growth of electrical trees in a model transparent silicone rubber were investigated using a new system recently developed at Southampton. With increasing voltage the trees became more complex in appearance but nevertheless grow more rapidly. As the tree evolves the PD pattern becomes more intense which may provide a method of monitoring the extent of treeing in opaque samples. Raman studies indicate that treeing and breakdown channels are hollow, carbonaceous entities, a finding consistent with other studies

Preliminary design of a Primary Loop Pump Assembly (PLPA), using electromagnetic pumps

A preliminary design study of flight-type dc conduction-permanent magnetic, ac helical induction, and ac linear induction pumps for circulating 883 K (1130 F) NaK at 9.1 kg/sec (20 lb/sec) is described. Various electromagnetic pump geometrics are evaluated against hydraulic performance, and the effects of multiple windings and numbers of pumps per assembly on overall reliability were determined. The methods used in the electrical-hydraulic, stress, and thermal analysis are discussed, and the high temperature electrical materials selected for the application are listed

Mean magnetic field generation in sheared rotators

A generalized mean magnetic field induction equation for differential rotators is derived, including a compressibility, and the anisotropy induced on the turbulent quantities from the mean magnetic field itself and a mean velocity shear. Derivations of the mean field equations often do not emphasize that there must be anisotropy and inhomogeneity in the turbulence for mean field growth. The anisotropy from shear is the source of a term involving the product of the mean velocity gradient and the cross-helicity correlation of the isotropic parts of the fluctuating velocity and magnetic field, \lb{\bfv}\cdot{\bfb}\rb^{(0)}. The full mean field equations are derived to linear order in mean fields, but it is also shown that the cross-helicity term survives to all orders in the velocity shear. This cross-helicity term can obviate the need for a pre-existing seed mean magnetic field for mean field growth: though a fluctuating seed field is necessary for a non-vanishing cross-helicity, the term can produce linear (in time) mean field growth of the toroidal field from zero mean field. After one vertical diffusion time, the cross-helicity term becomes sub-dominant and dynamo exponential amplification/sustenance of the mean field can subsequently ensue. The cross-helicity term should produce odd symmetry in the mean magnetic field, in contrast to the usually favored even modes of the dynamo amplification in sheared discs. This may be important for the observed mean field geometries of spiral galaxies. The strength of the mean seed field provided by the cross- helicity depends linearly on the magnitude of the cross-helicity.Comment: 15 pages, LaTeX, matches version accepted to ApJ, minor revision

COMPARING MANAGEMENT SYSTEMS FOR BEEF CATTLE BACKGROUNDING: A MULTIDISCIPLINARY APPROACH

Livestock Production/Industries,

Flux-transport dynamos with Lorentz force feedback on differential rotation and meridional flow: Saturation mechanism and torsional oscillations

In this paper we discuss a dynamic flux-transport dynamo model that includes the feedback of the induced magnetic field on differential rotation and meridional flow. We consider two different approaches for the feedback: meanfield Lorentz force and quenching of transport coefficients such as turbulent viscosity and heat conductivity. We find that even strong feedback on the meridional flow does not change the character of the flux-transport dynamo significantly; however it leads to a significant reduction of differential rotation. To a large degree independent from the dynamo parameters, the saturation takes place when the toroidal field at the base of the convection zone reaches between 1.2 an 1.5 T, the energy converted intomagnetic energy corresponds to about 0.1 to 0.2% of the solar luminosity. The torsional oscillations produced through Lorentz force feedback on differential rotation show a dominant poleward propagating branch with the correct phase relation to the magnetic cycle. We show that incorporating enhanced surface cooling of the active region belt (as proposed by Spruit) leads to an equatorward propagating branch in good agreement with observations.Comment: 15 pages, 12 figures, Accepted for publication in ApJ August 10 issue; corrected typos, corrected referenc

Magnetic Reversal in Nanoscopic Ferromagnetic Rings

We present a theory of magnetization reversal due to thermal fluctuations in thin submicron-scale rings composed of soft magnetic materials. The magnetization in such geometries is more stable against reversal than that in thin needles and other geometries, where sharp ends or edges can initiate nucleation of a reversed state. The 2D ring geometry also allows us to evaluate the effects of nonlocal magnetostatic forces. We find a `phase transition', which should be experimentally observable, between an Arrhenius and a non-Arrhenius activation regime as magnetic field is varied in a ring of fixed size.Comment: RevTeX, 23 pages, 7 figures, to appear in Phys. Rev.

Continuation of Unintended Pregnancy.

Background: Forty-four percent of all pregnancies worldwide are unintended. Induced abortion has drawn a lot of attention from clinicians and policy makers, and the care for women requesting it has been covered in many publications. However, abortion challenges the values of many women, is associated with negative emotions, and has its own medical complications. Women have the right to discuss their unintended pregnancy with a clinician and receive elaborate information about other options to deal with it. Continuing an unintended pregnancy, and receiving the necessary care and support for it, is also a reproductive right of women. However, the provision of medical information and support required for the continuation of an unintended pregnancy has hardly been approached in the medical literature. Objective: This review presents a clinical approach to unintentionally pregnant patients and describes the information and support that can be offered for the continuation of the unintended pregnancy. Discussion: Clinicians should approach patients with an unintended pregnancy with a sympathetic tone in order to provide the most support and present the most complete options. A complete clinical history can help frame the problem and identify concerns related to the pregnancy. Any underlying medical or obstetric problems can be discussed. A social history, that includes the personal support from the patient's partner, parents, and siblings, can be taken. Doctors should also be alert of possible cases of violence from the partner or child abuse in adolescent patients. Finally, the clinician can provide the first information regarding the social care available and refer the patients for further support. For women who continue an unintended pregnancy, clinicians should start antenatal care immediately. Conclusion: Unintentionally pregnant women deserve a supportive and complete response from their clinicians, who should inform about, and sometimes activate, all the resources available for the continuation of unintended pregnancy. Summary: Forty-four percent of all pregnancies worldwide are unintended. Induced abortion has drawn a lot of attention and the care for women requesting it has been covered in many publications. However, abortion challenges the values of many women, is associated with negative emotions, and has its own medical complications. Women have the right to discuss their unintended pregnancy with a clinician and receive elaborate information about other options to deal with it. Continuing an unintended pregnancy, and receiving the necessary care and support for it, is also a reproductive right of women. However, the provision of medical information and support required for the continuation of an unintended pregnancy has hardly been approached in the medical literature. This review presents a clinical approach to unintentionally pregnant patients and describes the information and support that can be offered for the continuation of the unintended pregnancy. Clinicians should approach patients with an unintended pregnancy with a sympathetic tone. A complete clinical history can help frame the problem and identify concerns related to the pregnancy. Any underlying medical or obstetric problems can be discussed. A social history, that includes the personal support from the patient's partner, parents, and siblings, can be taken. Doctors should also be alert of possible cases of violence from the partner or child abuse in adolescent patients. Finally, the clinician can provide the first information regarding the social care available and refer the patients for further support. For women who continue an unintended pregnancy, clinicians should start antenatal care immediately