Secular Effects of Tidal Damping in Compact Planetary Systems

We describe the long-term evolution of compact systems of terrestrial planets, using a set of simulations that match the statistical properties of the observed exoplanet distribution. The evolution is driven by tidal dissipation in the planetary interiors, but the systems evolve as a whole due to secular gravitational interactions. We find that, for Earth-like dissipation levels, planetary orbits can be circularised out to periods of order 100 days, an order of magnitude larger than is possible for single planets. The resulting distribution of eccentricities is a qualitative match to that inferred from transit timing variations, with a minority of non-zero eccentricities maintained by particular secular configurations. The coupling of the tidal and secular processes enhance the inward migration of the innermost planets in these systems, and can drive them to short orbital periods. Resonant interactions of both the mean motion and secular variety are observed, although the interactions are not strong enough to drive systemic instability in most cases. However, we demonstrate that these systems can easily be driven unstable if coupled to giant planets on longer period orbits.Comment: 17 pages, 22 figures, 2 tables, submitted to Monthly Notices of the Royal Astronomical Societ

Odd Parity and Line Nodes in Non-Symmorphic Superconductors

Group theory arguments have been invoked to argue that odd parity order parameters cannot have line nodes in the presence of spin-orbit coupling. In this paper we show that these arguments do not hold for certain non-symmorphic superconductors. Specifically, we demonstrate that when the underlying crystal has a twofold screw axis, half of the odd parity representations vanish on the Brillouin zone face perpendicular to this axis. Many unconventional superconductors have non-symmorphic space groups, and we discuss implications for several materials, including UPt3, UBe13, Li2Pt3B and Na4Ir3O8.Comment: 4 page

Integral Battery Power Limiting Circuit for Intrinsically Safe Applications

A circuit topology has been designed to guarantee the output of intrinsically safe power for the operation of electrical devices in a hazardous environment. This design uses a MOSFET (metal oxide semiconductor field-effect transistor) as a switch to connect and disconnect power to a load. A test current is provided through a separate path to the load for monitoring by a comparator against a preset threshold level. The circuit is configured so that the test current will detect a fault in the load and open the switch before the main current can respond. The main current passes through the switch and then an inductor. When a fault occurs in the load, the current through the inductor cannot change immediately, but the voltage drops immediately to safe levels. The comparator detects this drop and opens the switch before the current in the inductor has a chance to respond. This circuit protects both the current and voltage from exceeding safe levels. Typically, this type of protection is accomplished by a fuse or a circuit breaker, but in order for a fuse or a circuit breaker to blow or trip, the current must exceed the safe levels momentarily, which may be just enough time to ignite anything in a hazardous environment. To prevent this from happening, a fuse is typically current-limited by the addition of the resistor to keep the current within safe levels while the fuse reacts. The use of a resistor is acceptable for non-battery applications where the wasted energy and voltage drop across the resistor can be tolerated. The use of the switch and inductor minimizes the wasted energy. For example, a circuit runs from a 3.6-V battery that must be current-limited to 200 mA. If the circuit normally draws 10 mA, then an 18-ohm resistor would drop 180 mV during normal operation, while a typical switch (0.02 ohm) and inductor (0.97 ohm) would only drop 9.9 mV. From a power standpoint, the current-limiting resistor protection circuit wastes about 18 times more power than the switch and the inductor configuration. In the fault condition, both the resistor and the inductor react immediately. The resistor reacts by allowing more current to flow and dropping the voltage. Initially, the inductor reacts by dropping the voltage, and then by not allowing the current to change. When the comparator detects the drop in voltage, it opens the switch, thus preventing any further current flow. The inductor alone is not sufficient protection, because after the voltage drop has settled, the inductor would then allow the current to change, in this example, the current would be 3.7 A. In the fault condition, the resistor is flowing 200 mA until the fuse blows (anywhere from 1 ms to 100 s), while the switch and inductor combination is flowing about 2 A test current while monitoring for the fault to be corrected. Finally, as an additional safety feature, the circuit can be configured to hold the switch opened until both the load and source are disconnected

Peptide probes for proteases - innovations and applications for monitoring proteolytic activity.

Proteases are excellent biomarkers for a variety of diseases, offer multiple opportunities for diagnostic applications and are valuable targets for therapy. From a chemistry-based perspective this review discusses and critiques the most recent advances in the field of substrate-based probes for the detection and analysis of proteolytic activity both in vitro and in vivo

Finite Element Analysis (FEA) of the Taper-Trunnion Interface in a Metal on Metal Hip Implant

Metal on metal total hip replacements are a common procedure in which the hip joint is replaced with a metal stem, a metal femoral head and a metal socket, usually made of titanium or cobalt chromium. The stem has a tapered region (trunnion) where the femoral head is impacted onto. This creates what is known as the taper-trunnion interface within a hip implant. However, these hip implants seem to be very susceptible to fretting corrosion, where the corrosive fluid environment of the body accelerates the process of wear between two contact surfaces. Previous research has suggested that the design parameters of the taper and the trunnion could have a significant effect on the amount of fretting corrosion that is occurring at this interface. The parameter that showed the most promise is angular mismatch, or the difference in angles between the taper and the trunnion. Utilizing finite element analysis, we tested five different degrees of angular mismatch using a simplified model of the interface. We then recorded the maximum contact stresses along with the measured micro-motion of the trunnion against the taper. Finally we report and compare the difference in fretting work done between the different angular mismatched specimens

Lactosylceramide galactosidase: Comparison with other sphingolipid hydrolases in developing rat brain

Four enzyme assays were carried out with brains from rats of age 4 days to about 320 days. The enzymes were acid hydrolases: lactosylceramide galactosidases, galactosylphenol galactosidase, glucosylceramide glucosidase,a nd sphingomyelin phosphocholine hydrolase. The first two activities (based on wet brain weight) rose with age until about 24 days, then declined moderately; this curve parallel somewhat the curve for ganglioside concentration in brain. It is suggested that this parallelism supports the idea that lysosomal enzymes function in normal turnover. The other two enzymes studied showed a steadily declining activity with increasing age. It was found that the brain cytosol contained 12% or less of the galactosidase activiti, the value increasing somewhat in older rats. Most of the particulate galactosidase activities could be dispersed by sonication. The similarities between the two galactosidase activities suggest that most of the hydrolysis of the galactosylphenol is carried out by the lactosylceramide hydrolase. A procedure is given for preparing [3H]lactosylceramide labeled in the galactose portion of the molecule and for the assay of its hydrolase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32942/1/0000325.pd

Design of TKR Tibial Insert for Bowlegged Gait

One of the causes associated with total knee replacement (TKR) surgery is abnormal gait. In these gait cases, however, the TKR does not solve the ultimate issue because abnormal gait still occurs, and similar excessive forces still occur on the knee. It is likely that the TKR will experience accelerated wear, and the individual may have to undergo a second TKR sometime in the future. For our purposes, bowleggedness is either the external rotation of the hip or excessive varus of the knee. It was hypothesized that the inability to internally rotate the hip increases adduction moment and medial compartment stresses. In order to test this hypothesis, we created an analytical model to determine forces and moments at the knee. Results supported our hypothesis. In attempt to decrease the elevated stresses in the medial compartment, we created several models which modified the tibial plastic of the ADVANCE® Medial Pivot Knee. We performed stress analyses in ABAQUS and conducted experiments on each of the models. Based on our results we recommend the thickened anterior medial cusp implant for those with external rotation and the angled tray implant for those with varus deformity

Type Ia Supernova Distances at z > 1.5 from the Hubble Space Telescope Multi-Cycle Treasury Programs: The Early Expansion Rate

We present an analysis of 15 Type Ia supernovae (SNe Ia) at redshift z > 1 (9 at 1.5 < z < 2.3) recently discovered in the CANDELS and CLASH Multi-Cycle Treasury programs using WFC3 on the Hubble Space Telescope. We combine these SNe Ia with a new compilation of 1050 SNe Ia, jointly calibrated and corrected for simulated survey biases to produce accurate distance measurements. We present unbiased constraints on the expansion rate at six redshifts in the range 0.07 < z < 1.5 based only on this combined SN Ia sample. The added leverage of our new sample at z > 1.5 leads to a factor of ~3 improvement in the determination of the expansion rate at z = 1.5, reducing its uncertainty to ~20%, a measurement of H(z=1.5)/H0=2.67 (+0.83,-0.52). We then demonstrate that these six measurements alone provide a nearly identical characterization of dark energy as the full SN sample, making them an efficient compression of the SN Ia data. The new sample of SNe Ia at z > 1 usefully distinguishes between alternative cosmological models and unmodeled evolution of the SN Ia distance indicators, placing empirical limits on the latter. Finally, employing a realistic simulation of a potential WFIRST SN survey observing strategy, we forecast optimistic future constraints on the expansion rate from SNe Ia.Comment: 14 pages, 5 figures, 7 tables; submitted to Ap

Type Ia Supernova Rate Measurements To Redshift 2.5 From CANDELS: Searching For Prompt Explosions In The Early Universe

dThe Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) was a multi-cycle treasury program on the Hubble Space Telescope (HST) that surveyed a total area of -0.25 deg2 with -900 HST orbits spread across five fields over three years. Within these survey images we discovered 65 supernovae (SNe) of all types, out to z 2.5. We classify -24 of these as Type Ia SNe (SNe Ia) based on host galaxy redshifts and SN photometry (supplemented by grism spectroscopy of six SNe). Here we present a measurement of the volumetric SN Ia rate as a function of redshift, reaching for the first time beyond z =- 2 and putting new constraints on SN Ia progenitor models. Our highest redshift bin includes detections of SNe that exploded when the universe was only -3 Gyr old and near the peak of the cosmic star formation history. This gives the CANDELS high redshift sample unique leverage for evaluating the fraction of SNe Ia that explode promptly after formation ( 40 Myr. However, mild tension is apparent between ground-based low-z surveys and space-based high-z surveys. In both CANDELS and the sister HST program CLASH (Cluster Lensing And Supernova Survey with Hubble), we find a low rate of SNe Ia at z > 1. This could be a hint that prompt progenitors are in fact relatively rare, accounting for only 20% of all SN Ia explosions-though further analysis and larger samples will be needed to examine that suggestion. Key words: infrared: general - supernovae:Astronom