Determination of the rare earths, yttrium and scandium in silicate rocks and four new geological reference materials by electrothermal atomization from graphite and tantalum surfaces.

An improved graphite furnace atomic-absorption method has been developed for the determination of Sc, Y and the rare-earth elements in silicate rocks and related materials. The method, which involves the separation of the lanthanides by ion-exchange followed by their determination by electrothermal atomization, with use of an automatic sampling device, is more rapid than a previous method based on separation by co-precipitation with calcium oxalate and hydrous ferric oxide followed by normal injection of the solution into the furnace. Greater sensitivity (~ 10-40-fold) for La, Ce, Pr, Gd, Tb and Lu is also achieved by using a tantalum foil-lined graphite furnace instead of a pyrolytically-coated furnace. Results obtained for five international reference rock samples, NIM-G, SCo-1, MAG-1, SDC-1 and BHVO-1, are compared with those obtained previously by the oxalate-hydrous oxide co-precipitation method and with other published values. Results are given for four new Canadian iron-formation reference materials, FeR-1 to FeR-4.

Determination of scandium, yttrium and lanthanides in silicate rocks and four new canadian iron-formation reference materials by flame atomic-absorption spectrometry with microsample injection.

Enhancement of sensitivity by factors of up to 1.5 by use of the microsampling technique, coupled with the advantage of using small samples in small solution volumes, permits rapid flame AAS determination of traces of Sc, Y, Nd, Eu, Dy, Ho, Er, Tm and Yb in ultramafic and most other rocks of low rare-earth content, which would be either impossible or very difficult to analyse by direct aspiration because of the need for much larger sample weights and solution volumes. The rare-earths are separated by a modified ion-exchange or a double calcium oxalate and single hydrous ferric oxide co-precipitation procedure, and ultimately determined in an ethanolic perchlorate solution, buffered with 1% lanthanum, by the flame microsample injection technique, with a nitrous oxide-acetylene flame. The results obtained by this technique for six international reference rocks SY-2 (syenite), BCR-1 (basalt), BHVO-1 (Hawaiian basalt), SCo-1 (cody shale), MAG-1 (marine mud) and STM-1 (syenite) are compared with those obtained previously by the direct aspiration method and with other reported data. Results are given for four new Canadian iron formation reference materials FeR-1 to FeR-4.

Determination of cerium in silicate rocks by electrothermal atomization in a furnace lined with tantalum foil Application to 19 international geological reference materials.

A 40-fold increase in sensitivity obtained by using a tantalum foil lining in a pyrolytically-coated graphite furnace permitted determination of low ppm levels of cerium in most silicate rocks. A preliminary preconcentration by oxalate and hydroxide co-precipitations was used before determination by use of a Varian GTA-95 atomizer coupled with an AA-475 spectrometer. The results for 3 synthetic and 19 international reference materials, including 4 new Canadian iron-formation reference materials, showed good recovery and satisfactory agreement with other published values.

Pulmonary function of Indian athletes and sportsmen: comparison with American athletes.

Studies were conducted to evaluate pulmonary functions in Indian athletes and sportsmen associated with different athletic events and games. It was found that swimmers were having significantly higher vital capacity (VC) and forced expiratory volume (FEV1) values than all other athletic groups studied. Results have been discussed keeping in view the physiological, functional and structural demands in various events. Pulmonary function values of Indian athletes have also been compared with American athletes of standardized height for a better appraisal of athletic potentiality in our athletes. The importance of athletic training from childhood have been ascribed to be the reason for superior lung volumes and capacities in US athletes.

Sensory receptors and their afferents in the caudal sympathetic nerve of the domestic duck.

The behavioural reactivity of the visceral receptors and their afferents in the caudal sympathetic nerve (part of synsacral sympathetic chain) of domestic duck (Anas platyrhynchos) was studied using electrophysiological techniques to examine their involvement in different physiological functions. In total, 114 single unit activities were recorded from the caudal sympathetic nerve of duck. Receptors were classified according to location: in the anal sphincter (32 units), in the mucous membrane of the cloaca (45 units), at the branching point of the blood vessels over the rectum and adjacent mesentery (10 units), at the base of the feather follicles in and around the vent (17 units), and in the ventral and lateral lower abdominal wall muscle (10 units). Both spontaneous and non-spontaneous receptors responded to mechanical stimuli; average frequency of discharge of non-spontaneous units being much higher. Most of these receptors were of the rapidly-adapting type. Only some receptors in the abdominal muscle layer, anal sphincter and mucous membrane of hind gut were of the slowly-adapting type. Some of the latter responded to intraluminal distension pressure. Except for responses to succinylcholine chloride by receptors in the abdominal wall muscles and some units in the external anal sphincter, mechanosensitive receptors were not responsive to chemical stimuli. The discharge rate of the receptors at the base of the feather follicles varied according to the strength of stimulus. Conduction velocity of the caudal sympathetic afferent fibres ranged from 2.5 to 45 m/sec.

Physiological factors associated with the success in marathon running.

Marathon running is the most gruelling athletic event in international sport. Success of well trained athlete largely depends upon his perfect coordination of movements in relation to speed and optimum physiological adjustments. In order to identify the physiological factors which play crucial contributory role in successful marathon runners an evaluation study was conducted on 7 successful Indian athletes from among many competitors. Results of the study were compared between the 1st and the 7th rankers vis-a-vis the world champion in this event. Results indicated that the maximal aerobic power and economy in 'work' involved in marathon running were most important factors for the success in this event. In addition, a comparison of the blood lactic acid level of Indian with that of the world champion revealed that the latter could sustain at 85% of his maximal aerobic power for 2 hours compared to 78% and 62% of 1st and 7th ranker Indian athletes. There was not much of a difference between the world and Indian champion in this respect. Further, thermoregulatory efficiency was also found to play an important contributory role in determining success in this event. It is considered that a suitable index incorporating all the above factors is likely to be the most appropriate screening procedure in the evaluation programme of marathon runners for the reasons as discussed.

Chemoreceptor sensitivity in adaptation to high altitude.

Studies were carried out in a group of 20 young male subjects to investigate the changes in chemoreceptor sensitivity during acclimatization to altitude. Their hypoxic sensitivity and carbon dioxide sensitivity were studied at Delhi, during acclimatization at 3500 m, and on return to sea level. Similar studies were also done in a group of 10 acclimatized lowlanders who stayed at 3500-4000 m for 12-14 months, and also on 10 high-altitude natives. The results showed no significant alteration in the hypoxic sensitivity of the lowlanders; but CO2 sensitivity was markedly elevated at altitude, both in sojourners and acclimatized lowlanders. The high-altitude natives showed less sensitivity to hypoxia, whereas the CO2 sensitivity was normal.

Chemoreceptor sensitivity and maladaptation to high altitude in man.

Studies were carried out to find out the role of chemoreceptor sensitivity in the causation of maladaptation syndromes on acute exposure to altitude. The experiments were done in two phases. In phase I, the responses in chemoreceptor sensitivity were studied in altitude acclimatized subjects and compared with those who suffered from either High Altitude Pulmonary Oedema (HAPO) or Acute Mountain Sickness (AMS). In Phase II, a similar comparison was done in two groups of subjects, one representing normal sojourners at 3,500 m and the other being subjects who had just recovered from HAPO. The first phase was done at Delhi; and the second at an altitude of 3,500 m. Parameters of assessment were hypoxic sensitivity, carbon dioxide sensitivity, ventilation (VE), respiratory frequency (Rf), forced vital capacity (FVC), forced expiratory volume at the first second (FEV1), heart rate (HR), blood pressure (BP), and oral temperature (Tor). The results showed significantly lower sensitivity to both hypoxia and carbon dioxide in maladapted subjects, as compared to those who were acclimatized in both the categories suggesting thereby that reduced chemoreceptor sensitivity might be an initiating factor in the causation of maladaptation syndromes at altitude.

Visceral receptors and their afferents in the caudal mesenteric nerve of the duck.

1. The behaviour and reactivities of visceral receptors to different mechanical and chemical stimuli in simple unit preparations from the caudal mesenteric nerve of adult ducks were studied to examine the physiological roles of such receptors. 2. In total, 83 single unit activities were recorded from the caudal mesenteric nerve. 3. Receptors were grouped according to their locations in different layers of the rectum as (i) over the branching points of the blood vessel or in the serosal layer, (ii) in the muscle layer or (iii) in the mucous membrane of the rectum. 4. All the receptors, both spontaneous and non-spontaneous, responded to mechanical probing. Receptors of the muscle layer responded to distension also and showed a slowly-adapting nature. Most of the receptors of the other two groups were of the rapidly-adapting type. 5. Conduction velocity ranged from 0.76 to 34.6 m/s. 6. Sympathetic afferent fibres from the hind gut ascend along the intestinal nerve and join the caudal mesenteric nerve via the colonic ganglion.

Alterations in aerobic-anaerobic proportions of metabolism during work in heat.

With a view to investigating the aerobic and anaerobic proportions of oxygen supply during different grades of muscular activity in varying thermal stress, studies have been conducted on six young healthy Indians naturally acclimatized to heat. The subjects were given submaximal exercises of 400, 500, and 600 kgm/min (equivalent to 65.40, 81.75, and 98.10 W) for 6 min on a bicycle ergometer in three different simulated conditions, i.e., comfortable, hot humid, and very hot humid. Their O2 consumption (VO2), pulmonary ventilation (VE) and heart rate (HR) were measured during rest and throughout the exercise period (6 min) and for 30 min post exercise. Blood lactate level (LA) was measured during rest and recovery. From these, the total O2 cost with aerobic and anaerobic proportions were calculated. Results indicated a significant increase in the total O2 cost for each exercise with increasing thermal stress, along with a significant increase in the anaerobic fraction and a decrease in the aerobic fraction. The increase in anaerobic contribution to the energy supply processes was further confirmed by a significant increase in relative O2 debt (l/kg) and in blood lactate level at each work load. Thus, a highly significant correlation (P < 0.001) was found between O2 debt contracted and increase in thermal stress. A significant fall in VO2 max was also observed in hot humid and very hot humid conditions as against comfortable temperature, with no change in HR max and VE max.