Evolutionary and Physical Properties of Meteoroids

Astrophysical models for meteoroid formation and stellar and planetary evolutions are developed from simulation composition studies

Image-orthicon spectra of Geminids in 1969

The spectra of 25 meteors, recorded with an image orthicon technique in December 1969, are studied in relation to similar records made in August of the same year. Of 19 Geminid meteors in the absolute visual magnitude range 0 to +2, only one showed any evidence of the forbidden line of oxygen at 5577 A, while all Perseid meteors recorded in August exhibited the oxygen line, a result of the large difference in geocentric velocity between the two showers. Atoms identified in faint Geminid meteors include neutral iron, magnesium, calcium and sodium. The molecular bands of nitrogen are also observed

An unusual meteor spectrum

An extraordinary spectrum of a meteor at a velocity of about 18.5 + or - 1.0 km/s was observed with an image orthicon camera. The radiant of the meteor was at an altitude of about 49 deg. It was first seen showing a yellow red continuous spectrum alone at a height of 137 + or - 8 km which is ascribed to the first positive group of nitrogen bands. After the meteor had descended to 116 + or - 6 km above sea level it brightened rapidly from its previous threshold brightness into a uniform continuum, the D-line of neutral sodium appeared, and at height 105 + or - 5 km all the other lines of the spectrum also appeared. The continuum remained dominant to the end. Water of hydration and entrained carbon flakes of characteristic dimension about 0.2 micron or less are proposed as constituents of the meteoroid to explain these phenomena

Oncogenic K-Ras suppresses IP₃-dependent Ca²⁺ release through remodeling of IP₃Rs isoform composition and ER luminal Ca²⁺ levels in colorectal cancer cell lines

The GTPase Ras is a molecular switch engaged downstream of G-protein coupled receptors and receptor tyrosine inases that controls multiple cell fate-determining signalling athways. Ras signalling is frequently deregulated in cancer underlying associated changes in cell phenotype. Although Ca2+ signalling pathways control some overlapping functions with Ras, and altered Ca2+ signalling pathways are emerging as important players in oncogenic transformation, how Ca2+ signalling is remodelled during transformation and whether it has a causal role remains unclear. We have investigated Ca2+ signalling in two human colorectal cancer cell lines and their isogenic derivatives in which the mutated K-Ras allele (G13D) has been deleted by homologous recombination. We show that agonist-induced Ca2+ release from intracellular stores is enhanced by loss of K-RasG13D through an increase in the ER store content and a modification of IP3R subtype abundance. Consistently, uptake of Ca2+ into mitochondria and sensitivity to apoptosis was enhanced as a result of KRasG13D loss. These results suggest that suppression of Ca2+ signalling is a common response to naturally occurring levels of K-RasG13D that contributes to a survival advantage during oncogenic transformation

The Sioux City Water Supply

A good water supply is one of the greatest boons man can possess. Notwithstanding this fact, it is the one thing above all others, almost, which is likely to receive the least attention. It is well known to those who have given the subject some study that the taste is no criterion by which to judge a water. So often have we known men to declare that a certain water was good because of its excellent taste, often due to chlorides, nitrates, etc., derived from sewage, or outhouses not far distant. So often men will provide their families with every comfort that modern applied science has made possible and yet unknowingly be using a contaminated water supply. This was recently well illustrated by a prosperous professional man of Sioux City who not long since built a new home in Morningside and furnished it with every modern convenience at a cost of several thousands of dollars. Instead of tapping the city water supply which was not far distant, he dug a well and within two or three rods of the well sank a large cesspool which receives the drain from the kitchen and water closet

Results of AC loss tests on twisted and untwisted HTSC tape exposed to an external field

This paper presents the results of magnetic losstests on twisted and untwisted 37 multifilaments tapes exposed to an alternating field at power frequencies. The losses are measured using calorimetric methods, which are capable of measuring losses in short tapes with the accuracy of several microwatts per centimeter of tape. The losses of the tape due to the longitudinal field of the untwisted tape agree well with theoretical calculations. The measurement results on the twisted filament tape, with 50-mm twist pitch, show that the losses are slightly lower than that in the untwisted tape. This is due to the reduction of the coupling losses between the filaments in the tape. It is also shown that in the presence of normal fields, the losses are about one order higher than for longitudinal fields because of the anisotropic properties of the superconducting parts and because of the existence of eddy current loss in the silver sheath

Detection Techniques of Microsecond Gamma-Ray Bursts using Ground-Based Telescopes

Gamma-ray observations above 200 MeV are conventionally made by satellite-based detectors. The EGRET detector on the Compton Gamma Ray Observatory (CGRO) has provided good sensitivity for the detection of bursts lasting for more than 200 ms. Theoretical predictions of high-energy gamma-ray bursts produced by quantum-mechanical decay of primordial black holes (Hawking 1971) suggest the emission of bursts on shorter time scales. The final stage of a primordial black hole results in a burst of gamma-rays, peaking around 250 MeV and lasting for a tenth of a microsecond or longer depending on particle physics. In this work we show that there is an observational window using ground-based imaging Cherenkov detectors to measure gamma-ray burst emission at energies E greater than 200 MeV. This technique, with a sensitivity for bursts lasting nanoseconds to several microseconds, is based on the detection of multi-photon-initiated air showers.Comment: accepted for publication in the Astrophysical Journa

Flammable Gas Emissions in South African Gold and Platinum Mines Review of Incidents and Accidents

Flammable gas emissions are relatively common and widespread across the South African gold and platinum mines, but a general lack of awareness has lead to an increase in flammable gas related accidents and fatalities over the last ten years. The gas is usually a mixture of hydrocarbons C1 to C4 with hydrogen, each in varying quantities, with methane and hydrogen predominant. The three most common causes leading to gas accidents are changes to the ventilation, lack of testing for gas, and contraband, with gas ignitions caused by contraband and illegal tampering with caplamps. Development work accounts for 70 percent of all accidents, with only 11 percent of all reported emissions in stopes