A GIT interpretration of the Harder-Narasimhan filtration

An unstable torsion free sheaf on a smooth projective variety gives a GIT unstable point in certain Quot scheme. To a GIT unstable point, Kempf associates a "maximally destabilizing" 1-parameter subgroup, and this induces a filtration of the torsion free sheaf. We show that this filtration coincides with the Harder-Narasimhan filtration.Comment: 19 pages; Comments of the referees and references added. The construction for holomorphic pairs (Sections 6 and 7 from previous version) will appear in a further publication. To appear in Rev. Mat Complutens

Portable propellant cutting assembly, and method of cutting propellant with assembly

A propellant cutting assembly and method of using the assembly to cut samples of solid propellant in a repeatable and consistent manner is disclosed. The cutting assembly utilizes two parallel extension beams which are shorter than the diameter of a central bore of an annular solid propellant grain and can be loaded into the central bore. The assembly is equipped with retaining heads at its respective ends and an adjustment mechanism to position and wedge the assembly within the central bore. One end of the assembly is equipped with a cutting blade apparatus which can be extended beyond the end of the extension beams to cut into the solid propellant

Move of a large but delicate apparatus on a trailer with air-ride suspension

When valuable delicate goods are shipped by truck, attention must be paid to vibrations that may cause damage. We present a case study of moving an extremely delicate 6230-kg superconducting magnet, immersed in liquid nitrogen, from Livermore, CA to Seattle, WA showing the steps of fatigue analysis of the load, a test move, and acceleration monitoring of the final move to ensure a successful damage-free transport

A SQUID-based microwave cavity search for dark-matter axions

Axions in the micro eV mass range are a plausible cold dark matter candidate and may be detected by their conversion into microwave photons in a resonant cavity immersed in a static magnetic field. The first result from such an axion search using a superconducting first-stage amplifier (SQUID) is reported. The SQUID amplifier, replacing a conventional GaAs field-effect transistor amplifier, successfully reached axion-photon coupling sensitivity in the band set by present axion models and sets the stage for a definitive axion search utilizing near quantum-limited SQUID amplifiers.Comment: 4 pages, 5 figures, submitted to PR

Geriatric screening in first opinion practice: results from 45 dogs

Objectives To evaluate and report the results of screening geriatric dogs in a first opinion practice. Methods A prospective health screen of dogs over nine-years-old involving history taking, physical examination and urinalysis. Results At least one previously unrecognised problem was identified in 80% of 45 dogs and 353 findings (mean 7·8 per dog) were recorded. Owners often failed to recognise and report serious signs of age-related disease. However, they most often reported increased sleeping (31%), loss of hearing (29%) or sight (20%), stiffness or lameness (22%) and “slowing down” (20%). Increased lens opacity (64%), increased thirst (58%), pain (24%), increased frequency of urination (24%), signs of osteoarthritis (24%) and dental disease (22%) were most frequently identified at the time of consultation. Potentially, life-threatening findings included respiratory distress, palpable abdominal masses and metastatic lung disease. Screening resulted in 29 further diagnostic procedures, including 10 dental procedures, seven medical treatments, two surgical procedures and euthanasia of two dogs. Clinical Significance Screening elderly dogs identified unrecognised and unreported health risk factors resulting in lifestyle modification and ongoing monitoring, as well as signs of age-related diseases resulting in diagnostic investigations, early diagnoses and surgical and medical interventions to improve quality of life

A Search for Scalar Chameleons with ADMX

Scalar fields with a "chameleon" property, in which the effective particle mass is a function of its local environment, are common to many theories beyond the standard model and could be responsible for dark energy. If these fields couple weakly to the photon, they could be detectable through the "afterglow" effect of photon-chameleon-photon transitions. The ADMX experiment was used in the first chameleon search with a microwave cavity to set a new limit on scalar chameleon-photon coupling excluding values between 2*10^9 and 5*10^14 for effective chameleon masses between 1.9510 and 1.9525 micro-eV.Comment: 4 pages, 3 figure

Boundary-layer friction in midlatitude cyclone

Results from an idealized three-dimensional baroclinic life-cycle model are interpreted in a potential vorticity (PV) framework to identify the physical mechanisms by which frictional processes acting in the atmospheric boundary layer modify and reduce the baroclinic development of a midlatitude storm. Considering a life cycle where the only non-conservative process acting is boundary-layer friction, the rate of change of depth-averaged PV within the boundary layer is governed by frictional generation of PV and the flux of PV into the free troposphere. Frictional generation of PV has two contributions: Ekman generation, which is directly analogous to the well-known Ekman-pumping mechanism for barotropic vortices, and baroclinic generation, which depends on the turning of the wind in the boundary layer and low-level horizontal temperature gradients. It is usually assumed, at least implicitly, that an Ekman process of negative PV generation is the mechanism whereby friction reduces the strength and growth rates of baroclinic systems. Although there is evidence for this mechanism, it is shown that baroclinic generation of PV dominates, producing positive PV anomalies downstream of the low centre, close to developing warm and cold fronts. These PV anomalies are advected by the large-scale warm conveyor belt flow upwards and polewards, fluxed into the troposphere near the warm front, and then advected westwards relative to the system. The result is a thin band of positive PV in the lower troposphere above the surface low centre. This PV is shown to be associated with a positive static stability anomaly, which Rossby edge wave theory suggests reduces the strength of the coupling between the upper- and lower-level PV anomalies, thereby reducing the rate of baroclinic development. This mechanism, which is a result of the baroclinic dynamics in the frontal regions, is in marked contrast with simple barotropic spin-down ideas. Finally we note the implications of these frictionally generated PV anomalies for cyclone forecasting

Risk Factors for Severe Renal Disease in Bardet-Biedl Syndrome

Bardet-Biedl syndrome is a rare autosomal recessive, multisystem disease characterized by retinal dystrophy, renal malformation, obesity, intellectual disability, polydactyly, and hypogonadism. Nineteen disease-causing genes (BBS1-19) have been identified, of which mutations in BBS1 are most common in North America and Europe. A hallmark of the disease, renal malformation is heterogeneous and is a cause of morbidity and mortality through the development of CKD. We studied the prevalence and severity of CKD in 350 patients with Bardet-Biedl syndrome-related renal disease attending the United Kingdom national Bardet-Biedl syndrome clinics to further elucidate the phenotype and identify risk indicators of CKD. Overall, 31% of children and 42% of adults had CKD; 6% of children and 8% of adults had stage 4-5 CKD. In children, renal disease was often detected within the first year of life. Analysis of the most commonly mutated disease-associated genes revealed that, compared with two truncating mutations, two missense mutations associated with less severe CKD in adults. Moreover, compared with mutations in BBS10, mutations in BBS1 associated with less severe CKD or lack of CKD in adults. Finally, 51% of patients with available ultrasounds had structural renal abnormalities, and 35% of adults were hypertensive. The presence of structural abnormalities or antihypertensive medication also correlated statistically with stage 3b-5 CKD. This study describes the largest reported cohort of patients with renal disease in Bardet-Biedl syndrome and identifies risk factors to be considered in genetic counseling