Bondi mass with a cosmological constant

The mass loss of an isolated gravitating system due to energy carried away by gravitational waves with a cosmological constant $\Lambda\in\R$ was recently worked out, using the Newman-Penrose-Unti approach. In that same article, an expression for the Bondi mass of the isolated system, $M_\Lambda$, for the $\Lambda>0$ case was proposed. The stipulated mass $M_\Lambda$ would ensure that in the absence of any incoming gravitational radiation from elsewhere, the emitted gravitational waves must carry away a positive-definite energy. That suggested quantity however, introduced a $\Lambda$-correction term to the Bondi mass $M_B$ (where $M_B$ is the usual Bondi mass for asymptotically flat spacetimes) which would involve not just information on the state of the system at that moment, but ostensibly also its past history. In this paper, we derive the identical mass-loss equation using an integral formula on a hypersurface formulated by Frauendiener based on the Nester-Witten identity, and argue that one may adopt a generalisation of the Bondi mass with $\Lambda\in\R$ \emph{without any correction}, viz. $M_\Lambda=M_B$ for any $\Lambda\in\R$. Furthermore with $M_\Lambda=M_B$, we show that for \emph{purely quadrupole gravitational waves} given off by the isolated system (i.e. when the "Bondi news" $\sigma^o$ comprises only the $l=2$ components of the "spherical harmonics with spin-weight 2"), the energy carried away is \emph{manifestly positive-definite} for the $\Lambda>0$ case. For a general $\sigma^o$ having higher multipole moments, this perspicuous property in the $\Lambda>0$ case still holds if those $l>2$ contributions are weak --- more precisely, if they satisfy any of the inequalities given in this paper.Comment: 29 pages, accepted for publication by Physical Review

Power saw

A power saw is disclosed for space or robotic operations with jaw members for clamping to a work piece by an operation of a lever arm. The saw assembly is slidably mounted on the jaw assembly and fed into the work piece by a hand operated feed screw. The saw assembly includes a motor and gear belt. A current sensing circuit provides a current signal which actuates colored lights to visually depict the load on the saw blade during the cutting operations

Characterization and flow of food and mineral powders : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Manawatū, New Zealand

Powders are important commodities across different industries, such as the food and pharmaceutical industries. In these industries, powders are usually made, mixed, milled, packaged, and stored; these operations require the powders to move and flow under desired conditions and different stress levels. Failure to flow will cause hindrances to production; therefore knowledge of powder flow or flowability is important. There is a constant demand for accurate, reliable, and robust measurement and characterization methods for powder flowability. Powders behave differently under varying conditions; the behaviour of a powder is influenced by particle size distribution, and powder handling and processing conditions. There is to date no one “standard” method to characterize powder flowability; it is common to use a variety of methods and devices to measure flow properties and provide insight into the behaviour and flow characteristics of powders under different conditions. The flow properties of model food and mineral powders were measured and assessed by shear testing, compression via tapping, fluidization, and powder tumbling. Shear testing was done with an annular shear cell following Jenike (1964) and Berry, Bradley and McGregor (2014). Compression via tapping was performed according to a procedure in the dairy industry (Niro, 1978) and the European Pharmacopoeia (Schüssele & Bauer-Brandl, 2003). Fluidization was used to measure powder bed expansion and bed collapse following the powder classification framework provided by Geldart and co-workers (Geldart, 1973; Geldart, Harnby, & Wong, 1984; Geldart & Wong, 1984, 1985). Powder tumbling was performed in a novel Gravitational Displacement Rheometer, GDR, which measured the motion and avalanche activity of powders that moved under their own weight when rotated in a cylinder at different drum speed levels. The flow data from each characterization method were evaluated individually with regards to particle size distribution and then assessed collectively. The findings presented and discussed include the i) demonstration of the dominant influence of surface-volume mean particle diameter on powder flow properties, ii) characterization of flowability based on Jenike’s arbitrary flow divisions, iii) development of new correlations for the estimation of powder cohesion and bulk density at low preconsolidation stresses, iv) demonstration of hopper outlet diameter as a measure of flowability, v) demonstration of the limited utility of Hausner ratio as a flowability index, vi) substantiation of von Neumann ratio as a sensitive and useful indicator for identifying the onset of bubbling in fluidized beds using bed pressure fluctuation data, and vii) demonstration of the utility of standard deviation of the GDR load cell signal as an indicator of powder avalanche activity. These findings provide improved understanding and knowledge of powder flowability; they can be used to assist and facilitate the development of new techniques and solutions relevant to the handling and processing of powders especially in the food and pharmaceutical industries

Infectious Bovine Rhinotracheitis Virus of Cattle and Buffaloes

Infectious bovine rhinotracheitis virus infection in cattle has been reported throughout the world. The study of infectious bovine rhinotracheitis in buffalo was very limited. There was no report on infectious bovine rhinotracheitis in cattle and buffalo in Malaysia. A serological study on the prevalence of infectious bovine rhinotracheitis in cattle and buffalo in 10 states of Peninsular Malaysia showed that 52.52 per cent of the cattle and 65.07 per cent of the buffaloes had neutralizing antibodies to infectious bovine rhinotracheitis virus. Neutralizing antibodies were detected in 532 out of the 1013 serum samples from cattle and in 298 out of the 458 serum samples from buffaloes. The titre of the serum neutralizing antibodies ranged from 1:4 to 1:256. Four cattle and four buffaloes with neutralizing antibodies to infectious bovine rhinotracheitis virus were treated with dexamethazone at 0.1mg. per kilogram of body weight for 7 consecutive days. Treatment of these animals with dexamethazone resulted in shedding of virus. Viruses were isolated from nasal cavities and vaginas of the cattle and buffaloes in bovine embryonic kidney cells. The isolates were identified as infectious bovine rhinotracheitis virus by virus neutralizationtest. The viruses isolated from nasal cavity and vaginal mucosa of buffaloes were designated UPM BB 1 and UPM BB 2 respectively while the viruses isolated from nasal cavity and vaginal mucos a of cattle were designated UPM Be 1 and UPM Be 2 respectively. The 4 virus isolates had infective titres ranging from 10^6.8 to 10^7.8 Pfu per mL. The four infectious bovine rhinotracheitis virus isolates were then subjected to 3 cycles of plaque purification. The cloned infectious bovine rhino tracheitis viruses were further purified by rate zonal ultracentrifugat ion in 10 to 40 percent potassium tartrate. Examination of purified viruses under the electron microscope revealed virus morphology similar to that of herpes virus. The four purified virus preparations were also identified as infectious bovine rhinotracheitis virus by immune electron microscopy

Today I saw wolfmoon

Poetry by Matt Del Busto. Finalist in the 2019 Manuscripts Poetry Contest