FROM THE ARCHIVES
From the archives
Vol. II]
SEPTEMBER 1933
[NO. 3
Biology: Its importance in Modern Education One of the most important and remarkable developments of modern times has been in the study of Biology. Educated men have only very recently recognized the fact that this science is in a large sense the foundation of nearly all forms of human progress. In the past few years vast advances have been made in all the sciences, and in the realm of the Physical Sciences particularly, investigations and discoveries and their practical application to production have resulted in an immense increase of material wealth. This increase, however, is swallowed up by the drain due to the destructive activities of animals and plants which as parasites, carriers of disease germs, and destroyers of crops, are slowly gaining a dominance in the world. Their activities are a menace which unless checked may lead ultimately to the degeneration of the human race. We are awakening to the
fact that human efforts in checking this colossal drain on the wealth of nations can only be successful if undertaken on a national basis. A nation’s health and efficiency is the health and efficiency of its citizens, and unless this is of a high standard national wealth and prosperity will suffer. The first step in this great campaign is the education of the general public in the fundamental principles governing life – the laws of health, the functions of the body in health and disease, the chief types of animals and plants beneficial or dangerous to human health, the role of animals and plants in the spread of disease and the dangers of uncontrolled human reproduction, especially in the undesirable classes of humanity. Mass ignorance in these respects has undermined the health of nations, incapacitated millions and endangered the health of the fit. The two main channels for the drain of the world’s wealth are through human disease and animal and plant pests, and the progress made hitherto by experts has been almost entirely in the field of cure rather than prevention. In the problem of disease we have left the task to the medical fraternity. It is impossible for medical men and other scientists alone, with all their knowledge, experience and willingness to serve, to combat disease brought about through ignorance. For every individual cured through the corporate knowledge
of doctors and other scientists, there are tens of others who contract disease through that arch enemy, ignorance. The need for more doctors and more money to heal the ever-increasing numbers of suffering humanity will obtain scant relief as along as we fail to change our methods of approaching the problem. A nation’s knowledge of the means of preventing disease is probably the biggest and most important step in man’s warfare with disease. In the problem of animal and plant pests similar conditions prevail. Crores of rupees are annually lost in India through the devastating depredations of insects alone. Add to this the wealth lost by other animal and plant pests and the figure far outstrips the wealth that can be accumulated through the combined achievements of all modern science. The world can never be adequately grateful to the workers in the physical sciences whose achievements and discoveries have contributed much to the progress and prosperity of the world. Admirable as the progress and effect of these achievements may be, the world has not yet found an effective check to the drain of human life and wealth. Indeed we owe it as a tribute to these silent workers to specialize and concentrate on a study of the comparatively neglected Biological Sciences; a knowledge of which is absolutely essential for conserving the health and prosperity that the Physical Sciences have won for us.
OPINION
A review of coalbed methane exploration and exploitation Anirbid Sircar Methane is an unpleasant explosive contaminant of coal, better known for killing miners than benefiting society. But recent technology developed in the US has allowed the gas to be tapped and sold in commercial quantities. The 404
amount of methane held in coal seam depends on the age, moisture content and depth of the coal. Coal is a carbon-rich material that has been formed by the chemical and thermal alteration of organic debris. During
this process called coalification, a series of by-products are generated, including water and methane. With the progress of coal in rank from peat to anthracite, about 140 m3 of methane is generated per ton of coal. The amount of methane
CURRENT SCIENCE, VOL. 79, NO. 4, 25 AUGUST 2000
OPINION produced during coalification generally exceeds the capacity of coal to hold the gas. The excess gas migrates into the surrounding rock strata and into the traditional sand reservoirs that may overlie the more deeply buried coals. Methane can be extracted from the coal seams by the process of desorption according to which the initial reservoir pressure is reduced, by dewatering, to the critical desorption pressure. Thereafter, the coal seams release methane gas as the pressure is reduced. The abandonment pressure is the lowest pressure at which no more methane can be produced. Before an exercise of drilling for the purpose of methane extraction can be undertaken, an estimate of the reserves of coalbed methane gas is made.
Geological set-up in exploration From the geological mapping and the grade of the coal seams, a preliminary idea can be obtained whether coalbed methane has been formed, and if formed, entrapped in the coal bed. An idea of the cost of drilling for the purpose of extracting coalbed methane gas can also be obtained. Once the total coal thickness is known by mapping, its multiplication by the area extent gives the volume of coal which when multiplied by density gives the tonnage of coal. The coal tonnage upon multiplication by the gas content of coal, gives the amount of methane absorbed by the coal. The efficient gas recovery depends upon a large number of factors which in turn influence gas and water production. Of these only three factors, namely permeability, static reservoir pressure and gas desorption pressure are influenced to a greater extent 1.
Geophysical inputs Remote sensing imagery Remote sensing data to identify the major lineaments and tectonic set-up may be useful to explore an area of coalbed methane. The details of major fault trends will help in prioritizing the areas available for exploration.
Seismic survey High resolution seismic survey is helpful to know the basin configuration, its
tectonic style, thickness of coal-bearing formation, lateral continuity and approximate depth of different coal seams. The sampling interval, geophone, charge size, charge depth, group interval and shot interval should be carefully chosen through experiments and the full spectrum of recorded frequencies during processing of data should be retained. The geophysical inputs may, however, be required in a virgin field before taking up an area for coalbed methane exploration.
Drilling The design and procedure for drilling a coalbed methane gas well must achieve the aims of maintaining well control and preventing formation damage 2. The primary concerns for drilling are overpressure of gas/water kicks, high permeability which leads to loss of circulation fluid, formation damage due to the nature of coal and hole sloughing. The rigs commonly used are portable, self-propelled and hydraulically-driven, having a top head drive or a kelly drive. A major problem during drilling could be the excessive water flow. Drilling with pressure may be hindered due to escape of large quantities of water through the coal seams.
Worldwide interest At the moment, almost all of the world’s 7.6 bcm/y production of coalbed methane comes from the US 3, where reserves of coalbed methane are conservatively estimated at a third of natural gas reserves. Drilling is concentrated in two areas, Alabama’s Black warrior, where the coal seams are particularly gas-rich; and New Mexico’s San Juan basin, which is tied into the natural gas grid 4. Australia is likely to be the next producer of commercial quantities of methane: a couple of pilot projects in Queensland and New South Wales are already well advanced. However, one drawback in such a huge but sparsely populated territory is finding a market for the gas. China, the world’s largest coal producer, is sitting on more than 700 tcf of coalbed methane. The country already has a fairly widespread system of meth-
CURRENT SCIENCE, VOL. 79, NO. 4, 25 AUGUST 2000
ane drainage and capture, to keep its rather gassy mine safe enough to work in. But although 60% of drained methane is utilized, most of it is too dilute to be used in anything other than local power plants or factory sites. The smaller coal producers of the world are doing their bit for coalbed methane too. However, the mature industries and crowded territories of most of them will keep developments modest. Interest around the world is quickening, and world coalbed methane output is on the first track.
Coalbed potential of India India is among the top ten countries in coal resources, having an estimated coal reserve of 160 million metric tons, with an estimated methane resource of 850 BCM. The Indian coal is mainly confined to the Permian Gondwana basins and the tertiaries. Tertiary coals are widespread in Assam, Meghalaya, Arunachal Pradesh, Tamil Nadu, Rajasthan and Gujarat. Tertiary coals are generally found to be lignitic to sub-bituminous in rank and are generally considered to be unsuitable for coalbed methane target. However, tertiary coals in petroliferous basins of Cambay, Upper Assam and Assam–Arakan may be prospective due to reported higher gas content, which is probably stored in the coal after generation from deeper-lying hydrocarbon source beds or may be of biogenic origin. Methane emission studies from working mines of India reported most of the degree three gassy mines (> 10 cubic m/ton), are confined in the four Damodar Valley coal fields, viz. Raniganj, Jharia, Bokaro and North Karanpura in Bihar and West Bengal. In these areas, the thickest bituminous coals are extensively developed in the Barakar measurers and in Raniganj measures of Lower and Upper Permian age, respectively. The Barakar coal seams are superior to Raniganj coal seams as coalbed methane targets. Based on thickness and burial depth, rank and quality of coal has the greatest coalbed methane potential in India. Media reports have indicated that a few national and multinational companies have shown keen interest in coalbed methane exploration in India. 405
OPINION However, the companies which have already started work in field are Eassar Oil, ONGC, Reliance and CMPDIL.
Summary Coalbed methane exploration may open up a new energy industry in India. Evaluation of coal properties, construction of adsorption isotherm, and study of geological setting of coal basins should be an integral part of initial re-
search efforts. It is desirable to work out the techno-economic viability of a project after R&D efforts are completed and before exploration and exploitation are taken up.
3. Yates, K., Pet. Econ., 1998, 6, 11– 12. 4. Cooper, J. L. and Kumar, P., Integras 95, University of Alabama, Alabama, USA, 1995.
1. Mckee, C. R., Bumb, A. C. and Bell, G. J., SPE/DOE/GRI Paper 12858, Society of Petroleum Engineers, 1984, pp. 271– 281. 2. Hughes, B. D. and Logan, T. L., Pet. Eng. Int., 1999, 2, 16–20.
Anirbid Sircar is in the Tullow India Operations Ltd, 403-404 Gunjan Towers, Off Alembic-Gorwa Road, Subhanpura, Baroda 390 007, India e-mail:
[email protected]
SCIENTIFIC CORRESPONDENCE
Usefulness of dipstick test (ParaSightTMF) in high-risk groups for Plasmodium falciparum in Central India* A simplified detection assay that uses a dipstick (ParaSight TM F) developed by Becton Dickinson Advanced Diagnostics (Sparks, MD, USA) was evaluated in the field in forest villages of India 1. Its simplicity of use suggested it could play an important role in field for the accurate diagnosis of Plasmodium falciparum infection. Therefore, we have introduced this technique to people who work in the field and report their experience of using this test in high-risk groups, i.e. infants, children and pregnant women in two districts of Madhya Pradesh (MP; Central India), where malaria is mesoendemic and epidemic prone. The study was conducted during high transmission season of P. falciparum (August–November) in 20 villages of district Jabalpur and Chhindwara (MP) in 1998. The procedure was explained by a Laboratory Technician to one Field Lab Assistant (FLA) who then performed the test under supervision three times. The FLA (A) then explained the test procedure to his colleagues (B and C) who later performed the test in field without supervision. All three FLAs were assigned different study groups, viz. A, infants (1 m to < 12 m),
*Paper presented in a meeting on ‘Informal consultation on Malaria Diagnostics at the Turn of the Century’ from 25 to 27 October 1999 in Geneva. 406
B, children (1 yr to < 5 yrs) and C, pregnant women. Finger-prick samples of blood were collected by the FLAs from all available infants and pregnant women with or without fever. The FLAs then performed the rapid ParaSight TM F test; however, in children only from fever cases. (Infants and pregnant women are highly vulnerable and together they represent the magnitude of malaria in an area. Further, infants are often without symptoms up to 6 months or more because of the mother’s immunity and pregnant women generally do not come for blood examination as medicines are harmful to the foetus. Hence all available infants and pregnant women were included.) Verbal consent was obtained from the parents of infants/children and from the woman herself or her husband to carry out the test. Simultaneously, a trained microscopist made thick and thin smears which were re-examined by an independent expert unaware of the previous results for qual-
ity control. Parasite density was counted against 200 WBC in thick film and parasitaemia was calculated by taking 8000 as the average WBC count by a standard method (Parasites/µl = No. of parasites × WBC count/no. of WBC counted). Of the 472 people of all age groups examined by both the methods, 139 were found by microscopy to be parasitaemic, 111 were infected with P. falciparum, 23 with P. vivax and 5 had mixed infection of P. vivax and P. falciparum. Mixed infections were analysed with P. falciparum. None of the 23 P. vivax cases detected by thick blood film examination gave a positive test. Overall, the dipstick was positive in 105 cases, including 5 mixed infections (Table 1) out of 116 cases (sensitivity, 90.5%), and negative in 331 out of 333 cases (specificity, 99.4%), giving a positive and negative predictive value of 98.1 and 96.8%, respectively (efficiency, 97%). Two (A and C) out of the
Table 1. Specificity and sensitivity of the dipstick ParaSight TM F test in diagnosing P. falciparum in field as compared to thick smear by a trained microscopist in field laboratory Microscopy Dipstick ParaSight Positive Negative Total a
TM
F test
Positive
a
105 11 116
Negative b
Total
2 331 333
107 342 449
Including 5 mixed infections of P. vivax and P. falciparum. P. vivax cases are not included.
b
CURRENT SCIENCE, VOL. 79, NO. 4, 25 AUGUST 2000
SCIENTIFIC CORRESPONDENCE Table 2. Performance of the dipstick ParaSight TM F test in diagnosing P. falciparum when used by field workers in remote villages of Jabalpur and Chhindwara in comparison with thick blood smear in field laboratory Field lab assistant District
A (Infants)
Village
Jabalpur Chhindwara
No. of cases screened No. of blood smears positive for P. falciparum No. of blood smears positive for P. vivax No. of dipstick positive cases No. of blood smears negative No. of dipstick negative cases a
B (Children)
C (Pregnant women)
Technician (Adults)
Jabalpur Chhindwara Jabalpur Chhindwara
Total
Jabalpur
Chhindwara
221
42
146
0
18
19
0
26
472
23 a
15
49 b
0
2c
9
0
18
116
11 25 187 196
4 15 23 27
5 38 92 108
0 0 0 0
2 2 14 16
1 9 9 10
0 0 0 0
0 18 8 8
23 107 333 365
Two mixed infections of P. vivax + P. falciparum; bOne mixed infection of P. vivax + P. falciparum; cTwo mixed infections of P. vivax + P. falciparum.
three FLAs performed the test on 263 infants and 37 pregnant women, respectively and were able to carry out the test without difficulty with excellent results. These FLAs discovered an epidemic of P. falciparum in Chhindwara as 15 out of 42 infants (36%) and 9 out of 19 pregnant women (47%) were positive for P. falciparum in mass blood survey. Subsequently, fever cases among adults were screened by a technician for malaria and 18 out of 26 adults (69%) were positive for P. falciparum (Table 2). However, one FLA (B) who had screened 146 children had some difficulty in interpreting weakly positive results. He was unable to assess properly the red line when it was faint (< 100 ± 2.0 µl range 90–250 parasite/µl). This worker reported a high number (11) of false negative results (Table 2). Similar results were obtained by village health workers in another study carried out in Tanzania 2. Further, two infants who were positive for P. falciparum by dipstick test were missed by the microscopist in the field, as the parasitaemia was very low (≤ 50 µl). Analysis of the results shows that where P. falciparum asexual parasitaemia is greater than 250 parasites/µl, the dipstick test is 100% sensitive. Subsequently, based on dipstick results, a team consisting of a medical officer and a supporting staff carried out point prevalence surveys in 13 villages of Chhindwara and revealed that out of 1813 blood smears, 169 were P. vivax and 1141 were P. falciparum, giving a slide positivity rate of 72% and P. falciparum percentage of 87% (unpublished results).
The WHO global malaria control strategy 3 recommends rapid diagnosis of malaria at the village or primary health care levels, so that effective treatment can be administered quickly to reduce morbidity and mortality. In point of fact, the ParaSight TM F test will support this strategy as it enables the field staff to make an immediate definitive diagnosis so that adequate therapy can be initiated without delay. Although the unit price ($1.20) of ParaSight TM F test 4 does not permit its extensive field use in malaria endemic areas of India where many patients need a fever screen, however, limited use of this test has great potential for high-risk groups in primary health care centres in difficult and inaccessible areas as in Chhindwara to prevent the spread of disease. Further, malaria control relies heavily on presumptive treatment of fever cases under Indian National Anti Malaria Programme. Because of lack of symptom specificity, a majority of the diagnosis is inaccurate with no resulting benefit to the people from the treatment. This results in wastage of drug supplies, which developing countries can ill afford5. This test not only helps to reduce the number of unnecessary treatments, but also provides a more rational diagnosis and the treatment. In addition, use of this test has great potential for high-risk groups in difficult and inaccessible areas to prevent morbidity and mortality. Thus the study has revealed that a rapid test which requires little technical experience or equipment would therefore be invaluable in the diagnosis of malaria, especially in countries where laboratory facilities are poor or non-
CURRENT SCIENCE, VOL. 79, NO. 4, 25 AUGUST 2000
existent. Although cost is a factor, it must be weighed against the cost of high morbidity and mortality in highrisk groups and it is the test which can prevent the epidemic. 1. Singh, N., Singh, M. P. and Sharma, V. P., Am. J. Trop. Med. Hyg., 1997, 56, 188–191. 2. Premji, Z., Minjas, J. N. and Shiff, C. J., Trans. R. Soc. Trop. Med. Hyg., 1994, 88, 418. 3. World Health Organization, mimeographed document CTD/MAL/EXP/92.3. WHO Global malaria control strategy, Ministerial Conference on Malaria, 26– 27 October 1992, Geneva. 4. Kilian, A. H. D., Mughusu, E. B., Kabagambe, G. and Von Sonnenburg, F., Trans. R. Soc. Trop. Med. Hyg., 1997, 91, 666–667. 5. Taylor, P. and Mtambu, S. L., Trans. R. Soc. Trop. Med. Hyg., 1986, 80, 12–19. ACKNOWLEDGEMENTS. This study was extension of WHO sponsored global project on ‘New Diagnostics’ carried out in 1994–1995. Part of these results is presented in a meeting on new diagnostics in Geneva on the invitation of WHO (25–27 October 1999). Thanks are due to K. B. Goswami, Medical Technologist, Becton Dickinson (USA) for providing test kit to carry out this work. Thanks are due to field staff and laboratory technician of Malaria Research Centre for assistance. Received 12 May 2000; revised accepted 19 June 2000
NEERU S INGH Malaria Research Centre, (Field Station), Medical College Building, Jabalpur 482 003, India e-mail:
[email protected] 407
