Ar-39-Ar-40 of achondrites: Evidence for a lunar-like cataclysm

The observation that the K-Ar, Pb-Pb, and Rb-Sr ages of a significant number of lunar highland rocks were reset in the interval of 4.1-3.8 Ga ago led to the concept of a cataclysmic bombardment of the moon during this period. An important consideration for understanding the early bombardment history of the solar system, including the moon, is whether evidence also exists in meteorites for resetting of radiometric ages by cataclysmic bombardment of their parent bodies. A comparison of Ar-39-Ar-40 ages of achondritic meteorites with ages of lunar highland rocks should help elucidate the nature of the early bombardment of the solar system. We are participating in various consortia studies of primarily Antarctic eucrites and howardites for which we measured Ar-39-Ar-40 ages of various clasts and matrix samples. The results of these studies are presented

Flexor Reflex Decreases during Sympathetic Stimulation in Chronic Human Spinal Cord Injury

A better understanding of autonomic influence on motor reflex pathways in spinal cord injury is important to the clinical management of autonomic dysreflexia and spasticity in spinal cord injured patients. The purpose of this study was to examine the modulation of flexor reflex windup during episodes of induced sympathetic activity in chronic human spinal cord injury (SCI). We simultaneously measured peripheral vascular conductance and the windup of the flexor reflex in response to conditioning stimuli of electrocutaneous stimulation to the opposite leg and bladder percussion. Flexor reflexes were quantified using torque measurements of the response to a noxious electrical stimulus applied to the skin of the medial arch of the foot. Both bladder percussion and skin conditioning stimuli produced a reduction (43–67%) in the ankle and hip flexor torques (p \u3c 0.05) of the flexor reflex. This reduction was accompanied by a simultaneous reduction in vascular conductance, measured using venous plethysmography, with a time course that matched the flexor reflex depression. While there was an overall attenuation of the flexor reflex, windup of the flexor reflex to repeated stimuli was maintained during periods of increased sympathetic activity. This paradoxical depression of flexor reflexes and minimal effect on windup is consistent with inhibition of afferent feedback within the superficial dorsal horn. The results of this study bring attention to the possible interaction of motor and sympathetic reflexes in SCI above and below the T5 spinal level, and have implications for clinicians in spasticity management and for researchers investigating motor reflexes post SCI

Cosmogenic Ar-36 from neutron capture by Cl-35 in the Chico L6 chondrite: Additional evidence for large shielding

The cosmic ray produced Ar-36/Ar-38 ratio measured in iron meteorites is about 0.65, but is not well determined for stone meteorites due to the common presence of trapped Ar or absorbed atmospheric Ar in bulk analysis. Almost all single-extraction measurements of stones give Ar-36/Ar-38 ratios intermediate between the trapped and air values of 5.3 and the expected cosmogenic value of about 0.65. The isotopic composition of Ar was measured for stepwise temperature release of both chondritic and melt portions of Chico. The Chico data suggest that for large chondrites, the cosmogenic Ar-36/Ar-38 ratio may well be higher than 0.65, and therefore the procedure of correcting bulk analysis results may underestimate the concentration of cosmogenic Ar-38. In this context we note that in analysis of many Antarctic chondrites observed that determined amounts of cosmogenic Ar-38 averaged about 13 percent too low in comparison to that expected from measurements of other cosmogenic species

Riccati parameter modes from Newtonian free damping motion by supersymmetry

We determine the class of damped modes \tilde{y} which are related to the common free damping modes y by supersymmetry. They are obtained by employing the factorization of Newton's differential equation of motion for the free damped oscillator by means of the general solution of the corresponding Riccati equation together with Witten's method of constructing the supersymmetric partner operator. This procedure leads to one-parameter families of (transient) modes for each of the three types of free damping, corresponding to a particular type of %time-dependent angular frequency. %time-dependent, antirestoring acceleration (adding up to the usual Hooke restoring acceleration) of the form a(t)=\frac{2\gamma ^2}{(\gamma t+1)^{2}}\tilde{y}, where \gamma is the family parameter that has been chosen as the inverse of the Riccati integration constant. In supersymmetric terms, they represent all those one Riccati parameter damping modes having the same Newtonian free damping partner modeComment: 6 pages, twocolumn, 6 figures, only first 3 publishe

Leg Sympathetic Response to Noxious Skin Stimuli is Similar in High and Low Level Human Spinal Cord Injury

Objective To determine if sympathetically mediated vasoconstriction in the lower extremities is injury level dependent. Although sympathetic responses have been measured in the limbs of people with high and low level SCI using blood flow measurements, including Doppler ultrasound and venous plethysmography, a direct comparison between injury levels has not been made. Methods Volunteers with chronic SCI were grouped according to injury level. Above T6: high level (HL, n = 7), and T6 and below: low level (LL, n = 6). All subjects had complete motor and sensory loss. Leg arterial flows were recorded by venous occlusion plethysmography, and continuous heart rate and mean arterial pressure (MAP) were measured. The conditioning stimulus consisted of transcutaneous stimulation to the arch of the contralateral foot. Results HL and LL subjects demonstrated a significant decrease in arterial conductance during stimulation with no significant difference found between groups. As expected, only group HL demonstrated a significant increase in MAP. Conclusions These results support our hypothesis that local (leg) sympathetic responses are similar for both high and low level SCI. Significance While low level SCI does not typically present with autonomic dysreflexia, bouts of increased reflex sympathetic activity could have ramifications for metabolism as well as renal and motor system functio

Leg Sympathetic Response to Noxious Skin Stimuli is Similar in High and Low Level Human Spinal Cord Injury

Objective To determine if sympathetically mediated vasoconstriction in the lower extremities is injury level dependent. Although sympathetic responses have been measured in the limbs of people with high and low level SCI using blood flow measurements, including Doppler ultrasound and venous plethysmography, a direct comparison between injury levels has not been made. Methods Volunteers with chronic SCI were grouped according to injury level. Above T6: high level (HL, n = 7), and T6 and below: low level (LL, n = 6). All subjects had complete motor and sensory loss. Leg arterial flows were recorded by venous occlusion plethysmography, and continuous heart rate and mean arterial pressure (MAP) were measured. The conditioning stimulus consisted of transcutaneous stimulation to the arch of the contralateral foot. Results HL and LL subjects demonstrated a significant decrease in arterial conductance during stimulation with no significant difference found between groups. As expected, only group HL demonstrated a significant increase in MAP. Conclusions These results support our hypothesis that local (leg) sympathetic responses are similar for both high and low level SCI. Significance While low level SCI does not typically present with autonomic dysreflexia, bouts of increased reflex sympathetic activity could have ramifications for metabolism as well as renal and motor system functio

Evaluation of a pulsed quasi-steady MPD thruster and associated subsystems

The performance of quasi-steady magnetoplasmadynamic (MPD) thrusters at high power levels is discussed. An axisymmetric configuration is used for the MPD thruster, with various cathode and anode sizes, over a wide range of experimental conditions. Thrust is determined from impulse measurements with current waveforms, while instantaneous measurements are made for all other variables. It is demonstrated that the thrust produced has a predominately self-magnetic origin and is directly proportional to the square of the current. The complete set of impulse measurement data is presented

The Call for Ethics Education

The aforementioned cases are fictitious, but situations similar to them happen daily in the lives of veterinarians. Anyone who thinks otherwise would be well-advised to look over 24 additional far-ranging cases and what should you do? options found on pp. 118- 125, vol. 9, no. 3 of the Journal of veterinary Medical Education. (The entire issue is the proceedings of the 8th Symposium on Veterinary Medical Education, entitled Exploring Ethical and Value Issues in Veterinary Medicine .) Veterinarians in all areas of the profession will, at one time or another, be placed in compromising situations and will be forced to deal with issues whose answers are less than black and white in composition

School Organization Placement for the Ninth Grade Student

The purpose of this study was to obtain information regarding the best placement of the ninth grade student in the school organizational pattern. Thirty-six superintendents, seventy-seven high school principals and sixty-four high school teachers, in the state of Washington, responded to a questionnaire-opinionnaire regarding the physical, intellectual, emotional and social maturity level of the ninth grade student. The results showed support for the ninth grade student to be in a four-year high school grade configuration

Procedural Due Process and the Rules of Evidence—Federal Impeachment of the Voucher Rules—Welcome v. Vincent, 549 F.2d 853 (2d Cir.), cert. denied, 97 S. Ct. 2960 (1977)

Appellant, Ernest Welcome, was convicted in a New York state supreme court on charges of murdering two real estate brokers in their Bronx office. Before indicting Welcome, the State tried another party, Albert Cunningham, for the same offenses. Cunningham had admitted his participation in the crimes to police, giving an accurate account of the date, time, and location of the shootings. After a separate evidentiary hearing, the state court held that his confession to police had been voluntary and thus was admissible against him. Nevertheless, the charges against Cunningham were dropped in mid-trial. At his trial, Welcome called Cunningham as a defense witness. On direct examination he testified that he and two men named Branch and Green had committed the crimes of which Welcome was accused, but on cross-examination Cunningham denied having had anything to do with the murders. When Welcome\u27s counsel attempted to impeach this repudiation by introducing Cunningham\u27s confession as a prior inconsistent statement, the trial court barred the testimony on the ground that the witness had not explicitly implicated the defendant and, therefore, under New York\u27s voucher rule could not be impeached by the party that had called him to the stand. Welcome appealed the ruling. He also sought a new trial when a witness for the prosecution later changed his story. When his request was denied, he took a second appeal. The New York Court of Appeals affirmed the conviction and dismissed the appeal from the motion for a new trial. Welcome thereupon petitioned for a writ of habeas corpus in the federal district court for the southern district of New York. The district court rejected his argument that the state\u27s refusal to permit cross-examination of Cunningham as to his confession and, alternatively, its refusal to grant him a new trial in the face of another witness\u27 recantation each constituted a deprivation of his fourteenth amendment due process right to a fundamentally fair trial. The Court of Appeals for the Second Circuit reversed. Held: When another person, present on the witness stand, has previously confessed that he, rather than the defendant on trial, has committed the crime, to restrict examination of such a witness so that his prior confession may not be proven is to deny the defendant a fair trial under the fourteenth amendment due process clause, at least when the confession, though retracted, has some semblance of reliability. Welcome v. Vincent, 549 F.2d 853 (2d Cir.), cert. denied, 97 S. Ct. 2960 (1977)