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A novel ignition system was studied experimentally, in which small volumes of hydrogen peroxide – of the order of µL/s – were injected at the site of ignition, during the firing of a focus discharge igniter. Experiments were made at an atmospheric testing facility using an industrial Rolls-Royce olympus combustion chamber with kerosene Jet A1 as the fuel and atmospheric air as the oxidizer. The study concentrated on the determination of the lean ignition limits of the Jet A1–air mixture at various air mass flowrates with and without the addition of H2O2. Notable improvements, from 6.5 per cent to 44 per cent, in the ignition limits of the kerosene–air mixture were attainable using only a small amount of H2O2 during the ignition process. The study suggests that these improvements are directly related to the increase in the ignition efficiency of the igniter.

High-resolution nuclear magnetic resonance (NMR) spectroscopy has been used for the past several years quite effectively in both the qualitative and quantitative determination of the molecular chain structures and compositions of various polymeric systems. Valuable structural information obtained from such NMR studies has included: (1) detailed stereo chemical configuration (both tacticities and stereoblock sizes) of the polymer chains, (2) copolymer compositions, (5) sequence distribution studies in copolymers, (4) determination of modes of monomer addition in both homopolymers and copolymers, and (5) extent of head-to-head structures. Currently, only H1 and F19 NMR techniques are being used in the elucidation of organic polymer structures, for reasons primarily of instrumental sensitivity but also involving general applicability. Examples of the utility of F19 and H1 NMR, as well as double-resonance techniques, to determine chain structure and composition of fluorine-containing polymers are presented in this paper. In particular, conclusive proof of a substantial amount (10–12%) of head-to-head structure and the detailed assignment of the F19 chemical shifts in poly(vinylidene fluoride) is presented. The existence of a very large amount (26–32%) of he ad-to-head structure in both experimental and commercial samples of poly(vinyl fluoride) is also shown (although the detailed assignment of the F19 NMR spectral peaks has not yet been completed); this indicates that about one monomer unit in every six or so is added “backwards” to the growing polymer chains during free-radical homopolymerizations. Increase in the amount of head-to-head structure with increase in polymerization temperature is also observed for poly(vinyl fluoride).

The disordered-molecular-alloy phase (DMA) of ammonia hydrates [J.S. Loveday and R. J. Nelmes, Phys. Rev. Lett. 83, 4329 (1999)] is unique in that it has substitutional disorder of ammonia and water over the molecular sites of a body centred cubic lattice. Whilst this structure has been observed in ammonia di- and mono-hydrate compositions, it has not been conclusively observed in the ammonia hemihydrate system. This work presents investigations of the structural behaviour of ammonia hemihydrate as a function of P and T. The indications of earlier studies [Ma et al. RSC Adv. 2, 4290 (2012)] that the DMA structure could be produced by compression of ammonia hemihydrate above 20 GPa at ambient temperature are confirmed. In addition, the DMA structure was found to form reversibly both from the melt, and on warming of ammonia hemihydrate phase-II, in the pressure range between 4 and 8 GPa. The route used to make the DMA structure from ammonia mono-and di-hydrates-compression at 170 K to 6 GPa followed by warming to ambient temperature-was found not to produce the DMA structure for ammonia hemihydrate. These results provide the first strong evidence that DMA is a thermodynamically stable form. A high-pressure phase diagram for ammonia hemihydrate is proposed which has importance for planetary modelling. (C) 2015 AIP Publishing LLC.

The structure of the crystalline ammonia-bearing phase formed when ammonia monohydrate liquid is compressed to 3.5(1) GPa at ambient temperature has been solved from a combination of synchrotron x-ray single-crystal and neutron powder-diffraction studies. The solution reveals that rather than having the ammonia monohydrate (AMH) composition as had been previously thought, the structure has an ammonia hemihydrate composition. The structure is monoclinic with spacegroup P2(1)/c and lattice parameters a = 3.3584(5) angstrom, b = 9.215(1) angstrom, c = 8.933(1) angstrom and beta = 94.331(8)degrees at 3.5(1) GPa. The atomic arrangement has a crowned hexagonal arrangement and is a layered structure with long N-D center dot center dot center dot N hydrogen bonds linking the layers. The existence of pressure-induced dehydration of AMH may have important consequences for the behaviour and differentiation of icy planets and satellites. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3686870]

To improve the information given to patients before endoscopy an audit was performed in 16 of 18 endoscopy units in Northern region. Details of current endoscopy information leaflets provided by the 16 respondents were discussed by nurses and consultants from the participating units, and a standard, including 12 separate items, was agreed. Each unit was provided with a comparison of its current leaflet with the standard, which highlighted areas for potential improvement. Six months later the participating units were again asked to provide details of the information; 13 replied, 11 of which had produced new leaflets and two which were in the process of doing so. In the initial survey only 35% (range 8-67%) of the items in the standard were included in the leaflets. Particular omissions were an indication of risks of procedures (three units), notification of follow up procedures (two), details for obtaining the results of the endoscopy (five), advice for people with diabetes (two) and providing a contact number for the endoscopy unit (four). In the repeat audit all 11 units had made changes to their leaflets and, overall, 80% of the items were included. Through this simple audit the range of information given to patients attending for endoscopy in the region has improved.

A delicate balance in host immunity is constantly maintained, allowing for potent responses during infection and quickly silencing these responses once infection resolves. Perturbations in this balance result in increased susceptibility to infection, immune cell-mediated injury to the host, or both. Part of the answer of better stabilizing our immune defense is the advent of vaccines. Although currently available vaccines for neonates use are able to elicit robust antibody responses, this type of response provides immunity for some infections; it does not provide immunity to pathogens, such as Listeria monocytogenes (Lm), that primarily reside in the intracellular compartment, which require antigen, specific Th1, and CD8 T cells. Lm is a major pathogen in the neonate and in other immune-compromised hosts, causing gastroenteritis, abortion, sepsis, and CNS infections. A recent discovery that could provide some answers could be a fraction of CD4 T cells, called T-regulatory cells (or simply Tregs), which have recently been identified to play an active regulatory role by suppressing the function of other CD4 and CD8 T cells. Neonatal cells do not respond well to some vaccines due to their natural bias toward a Th2 response; given the potential reactivity of fetal T cells, it seems reasonable to hypothesize that neonatal Tregs cells contribute to apparent fetal unresponsiveness by dominant tolerance mechanisms, perhaps to prevent destructive reactivity to maternal antigens. Preliminary data to ascertain this hypothesis indicated that neonatal murine Tregs transcriptionally expressed more of the foxp3 gene compared with adults Tregs per cell basis, and these data could lend themselves to function. Comparing the transfer of donor adult versus neonatal Tregs within the responder Lm-infected mice, we hope to test the ability of neonatal versus adult Tregs to suppress the action of same responder population (adult splenocytes) by measuring their ability to produce a Th1 cytokine (IFN-γ). Unfortunately, adult Tregs resulted in greater suppressive activity than their neonatal counterpart did.

The energy effects accompanying the processing of the feed material to a lead blast furnace are considered in terms of a reversible model. Relative to this model the efficiencies of operating furnaces are found to be in the range 18 to 35 pct. The effects of the effluent gas CO2/CO ratio and temperature and oxygen enrichment of the blast air in the thermodynamic efficiency are quantified. Improvements in efficiency achieved in industrial furnaces as a result of oxygen enrichment of the blast air are substantially greater than those predicted. Mass and enthalpy balances on an industrial lead blast furnace are presented from which it is estimated that approximately 9 pct of the carbon charged to the furnace is lost due to the solution loss reaction in the upper regions of the furnace.

A model is presented for the calculation of radiation-induced signals in multiconductor electrical cables. The model employs a Monte Carlo method for the calculation of the radiation-driven charge displacement within the cable and a Green's function to translate charge displacement into induced currents on conductors. The model, which is applicable to cables of arbitrary cross-sectional geometry and material configuration, permits consistent treatment of such effects as gaps, residual air, spatially-dependent transient conductivity arising from dose enhancement, saturation, and polarization-effects. These effects have, by improper treatment or neglect, limited the applicability and accuracy of previous models. Results are presented demonstrating the effects of gaps, residual air, dose enhancement, and dielectric liners and illustrating the distribution of signals on many-conductor cables.

Summary. The herbicidal activity and the tolerance of winter and spring cereals to ioxynil (4-hydroxy-3,5-diiodobenzonitrile)and bromoxynil(3,5-dibromo-4-hydroxybenzonitrile) as alkali metal and ammonium salts, have been determined in field experiments. Both compounds controlled most of the important weeds of cereals at doses between 3 and 8 oz a.i./ac. In seedling grass crops, where weeds were influenced less by crop competition, the effective dose range was 6–8 oz/ac. Some species normally resistant to the phenoxyalkanoic acid herbicides, including Stellaria media, Tripleurospermum marilimum and some Polygonum spp. were controlled by these herbicides. Ioxynil was generally more active than its dibromo analogue, particularly against Stellaria media. The activity of both compounds was improved by the addition of a wetting agent (0–02% sodium dinonyl sulphosuccinate) but activity was not influenced by changes in volume rate over the range 18–65 gal/ac. Perennial weeds were not affected by the doses needed for the control of annual weeds and rates of 16 oz/ac and above were necessary for the control of Cirsium arvense and Sonchus arvensis. The factors most likely to affect cereal tolerance are growth stage of crop and the addition of wetter to the spray solution. Neither ioxynil nor bromoxynil significantly affected grain yields when applied to spring and winter wheat, spring barley and oats at two to four times the rate necessary for weed control. On a total of five varieties of spring wheat and six varieties each of spring barley and oats applications of both compounds at doses up to 32 oz/ac caused only temporary and superficial leaf scorch. In only two out of twenty-five experiments was there more than slight scorch at doses below 16 oz/ac and these two cases do not significantly detract from the evidence of the high crop safety margin of these compounds. Etude en plein champ des facteurs influencant l'activite herbicide de l'ioxynil et da bromoxynil et la tolerance des cereales a ces deux herbicides Resume. L'activite herbicide de l'ioxynil (4-hydroxy-3,5-diiodobenzonitrile) et du bromoxynil (3,5-dibrorno-4 hydroxy benzonitrile) et la resistance des cereales d'hiver et de printemps a ces produits ont ete determinees en experimentation de plein champ. Les deux composes ont detruit la plupart des adventices importantes des cereales aux doses comprises entre 3 oz/ac (210 g/ha) et 8 oz/ar (560 g/ha). Dans les jeunes semis de graminees prairiales ou les mauvaises herbes etaient moins concurrencees par la culture, les doses efficaces etaient comprises entre 6 et 8 oz/ac (420–560 g/ha). Quelques especes, normalement resistantes aux herbicides du type acides phenoxyatcanoiqucs, telles que Stellaria media, Tripleurospermum maritimum et quelques Polygonum sp. furent detruites par ces herbicides. L'ioxynil etait generalement plus actif que son homologue dibrome, notamment contre Stellaria media. L'activite des deux produits etait accrue par l'addition d'un mouillant (0.02 % de dimonylsulfosuccinate de sodium), mais l'activite n'etait pas influencee par une variation du volume de bouillie pulverise, tout au moins entre les limites de 18 et 65 gal/ac (200–730 l/ha). Les mauvaises herbes perennes netaient pas affectees aux doses necessaires a la destruction des adventices annuelles; des doses de 16 oz/ac (1.120 kg/ha) et plus etaient necessairespour detruire Cirsium arvense et Sanchus arvensis. Le stade de croissance de la culture et l'addition d'un agent moullant a la bouillie sont les facteurs qui tres vraisembalement influencent le resistance des cereales. Ni l'ioxynil, ni le bromoxynil n'ont eu d'influence significative sur les rendements en grains lorsqu'ils ont ete appliques sur bles d'hiver et de printemps ou sur orges et avoines de printemps a des doses doubles ou quadruples de celles necessaires au desherbage de ces cultures. Sur un total de cinq varietes de bles de prin temps et de six varietes de chacune des cereales de printemps, orge et avoine, les applications des deux produits a des doses atteignant jusqu'a 32 oz/ac (2,240 kg/ha) produisirent seulement, sur fes feuilles, de legeres brulures temporaires et superficielles. Dans deux cas seulement sur vingt-cinq essais il a ete observe des bruulures un peu plus accentues a des doses inferieures a 16 oz/ac (1,12 kg/ha) mais ces deux cas ne permettent pas de douter de la grande marge de securite de ces produits pour les cultures. Feldversuche mit loxynil und Bromoxynil Zusammenfassung. In Feldversuchen wurde fur die Alkali- und Ammoniumsalze von Ioxynil (4-Hydroxy-3,5-dijod-benzonitril) und Bromoxynil (3,5-Dibrom-4-hydroxy-ben-zonitril) die herbizide Wirksamkeit und der Einfluss auf Winter- und Sommergetreide untersucht. In Aufwandmengen von 0,21 und 0,56 kg/ha A.S. vernichten beide Verbindungen die wichtigsten Getreideunkrauter gut. In Grasansaaten, in denen die Unkrauter durch die Kulturpflanzenkonkurrenz weniger stark beeinflusst werden, betrug die wirksame Konzentration 0,42 -0,56 kg/ha. Einige Arten wie Stellaria media, Tripleurospermum maritimum und verschiedene Polygonumarten, die normalerweise gegen Phenoxyfettsauren widerstandsfahig sind, wurden durch diese Herbizide bekampft. Ioxynil war gewohnlich wirksamer als sein Dibromanalog, was insbesondere bei Stellaria media auffallend war. Die Wirksamkeit beider Verbindungen wurde durch Netzmittel, nicht jedoch durch Veranderung der Spritzflussigkeit von 200-730 I/ha, erhoht, Aufwandmengen, die zur Bekanderung der einjahrigen Unkrauter ausreichten, waren gegen mehraahrige Arten unwirksam. gegen Cirsium arvense und sonchus arvensis waren 1,12 kg/ha und mehr fur eine befriedigende Bekampfung erforderlich. Die faktoren, die die schadigungsgefahr bei Getreide beeinflussen, sind im wesentlichen das Wuchsstadium der Kulturpflanze und der Zusatz von Netzmitteln zur Spritzflussigkeit. Weder Ioxynil noch Bromoxynil fuhrten in einer aufwandmenge, die das zwei- bis vierfache der zur Unkrautbekampfung erforderlichen Konzentration betrug, zu einer gesicherten Beeinflussung der Kornertrage von Sommer- und Winterweizen, Sommergerste und Hafer. Bei der Prufung von insgesamt funf Sommerweizensorten und je sechs Sommergersten- und Hafersorten verursachten beide Verbindungen in Aufwandmengen bis zu 2,24 kg/ha allenfalls vorubergend leichte Blattverbrennungen. In nur zwei von 25 Versuchen traten starkere Verbrennungen bei Aufwandmengen under 1,12 kg/ha auf, und diese beiden Falle konnen nicht als sicheres Argument gengen die hohe Unempfindlichkeit der Kulturpflanzen gegenuber diesen beiden Verbindungen angesehen werden.

It has been the custom for a considerable period, to investigate the dosage in radiation teletherapy, in a plane passing centrally through the site of the lesion to be irradiated, or at a number of points distributed throughout the lesion. The radiation fields employed are usually approximately symmetrical about a central axis, and the dosage-rate measurements have been made chiefly in a plane passing through this axis. A diagram of lines of equal dosage-rate (“isodose curves”) provided with the source of radiation has hitherto been regarded as a quantitative description of the field generated. In many cases, since this central plane can be made to coincide with the central plane of the lesion, the dose applied to the central parts of the tumour can be deduced from such diagrams. In some cases it is not possible, on account of the situation of the lesion, to make the two central planes coincide. In such cases arising in Westminster Hospital, the dose in the central plane (or any other plane) has been foun...

A series of measurements by Sievert's condenser chamber technique of the dosage, due to the 2-gramme radium bomb at Westminster Hospital, within a human cadaver are described and compared with similar measurements within a water phantom. It is shown that for sites extensively surrounded either by water or by human tissue, the dosage is identical. For regions near the boundaries of tissues, however, the dosage measured is different from that in an extensive water phantom. It is suggested that for such regions, a volume of water (or other phantom material) should be used, equivalent to that part of the body undergoing irradiation. In the irradiation of brain tumours it appears that the removal of the bone of the skull enhances the depth dose by 12–13 per cent.

An account is given of the construction of a compact 2-gramme radium teletherapy unit, which is also arranged to allow the safe removal of a special 1-gramme source for contact irradiation. Details are given of the radiation fields available from the unit for radium teletherapy.

Once more the time has arrived for the delivery of the Presidential Address. But for me the occasion is very different from any that went before. Previously I have been able, with great content, to sit back and listen to most interesting, well-delivered discourses on very many different aspects of the Institute, or its members, or their work. Tonight I am most conscious that I have the very great honour and privilege to deliver the address—and even more am I conscious of my inability to maintain the very high standards that have been set, upon this occasion, by my predecessors in this office. I must confess that in deciding finally upon the subject of my address, I have had some misgivings. A survey of past events, no matter how limited its scope, might probably come more fittingly from an older man than myself; but, I thought eventually, it cannot be other than a good thing, to remind ourselves, upon occasion, of the origins of an existing situation, possibly to draw encouragement in our present endeavou...

It is suggested that if the γ-ray dosage received by radium therapists during their radium work could be assessed (even if only roughly), more specific opinion might be formed as to what levels of exposure have proved to be safe. Calculations and measurements of local dosage and integral dose received by radium mould technicians and radium therapists are made in order to make such assessment. On the basis of these results the implications of the various proposed standards of protection are examined and set out in terms of actual working conditions. For this purpose protection is considered in the categories in which it seems the subject should be divided, viz., local exposure of the hands, local exposure of the gene material and integral dose throughout the whole body. In relation to medical work it is concluded (1) that many busy radium personnel may receive local exposure to the hands in excess of that now recommended in the U.S.A. as a safe amount (1 r per day), (2) that if circumstances dictate it sho...

The alternating copolymerization of bicyclo[2.2.1]hept-2-ene and sulfur dioxide has been found to be quite unusual for a free-radical polymerization: (1) the initiation of copolymerization is spontaneous, even at −40°C.; (2) solution copolymerization is extremely fast, yielding very high molecular weight polymer within a few seconds; (3) conversions are high (up to 93% within a minute); (4) molecular weight during copolymerization increases at essentially constant conversion; (5) the reaction is incapable of being chemically inhibited indefinitely, short of exhausting one of the constituent monomers; (6) at elevated temperatures, the monomers and copolymer appear to be in equilibrium; (7) large concentrations of free radicals have been detected by electron paramagnetic resonance to be associated with the bulk copolymerization; and (8) the copolymerization appears to result in “living” free-radical polymers. A copolymerization mechanism is proposed to explain these observations. Bicycloheptene and sulfur dioxide initially form a 1 : 1 molecular charge transfer complex which rearranges to a biradical; subsequent coupling of biradicals with each other (and possibly also with the molecular complexes themselves) leads to rapid propagation to high molecular weight, alternating copolymer. Speculations that similar mechanisms may be important in other copolymerization reactions are also made.

Nuclear magnetic resonance studies of the linear chain polymer polytetrafluoroethylene (Teflon) indicate the coexistence of two phases, each characterized by its own pair of relaxation times T1 and T2. Decomposition of the complex resonance lines and complex saturation curves into normal curves permits determination of the fraction of nuclei in each phase. It is suggested that the phases are the crystalline and amorphous regions of these polymers, and some additional evidence to support this suggestion is presented.The phase thought to be crystalline shows a marked line‐narrowing at the first‐order thermodynamic‐transition point near 293°K.The less complete data presented for polyethylene suggest the analogous presence of two phases, and the line‐shape analysis yields reasonable values for the degree of crystallinity.

(1905). The Camp of the Tenth Legion at Jerusalem and the City of AElia. Palestine Exploration Quarterly: Vol. 37, No. 2, pp. 138-144.

Since the last International Congress of Radiology in Chicago, in 1937, one feature of the development of radiology in this country has been the rapid increase in the number of hospital physicists whose work is chiefly connected with radiotherapy. Coincident with this increase, and not unrelated to it, there has been an increasing measure of collaboration between radiotherapist and hospital physicist in the design and realisation of radiotherapy techniques for the treatment of malignant disease. This close clinical association has certainly been of great educational value to the hospital physicist; it is to be hoped that the radiotherapist has also benefited similarly. In the short time at my disposal it is impossible to deal with more than one facet of this development and that only very inadequately. I have decided to try to outline some of the developments of the physical aspects of teleradium therapy which have occurred since 1937. To this end I shall deal with the subject under two main headings, viz...

A sensitive method of measuring small ionization currents is described, and the effect of secondary beta radiation upon ionization measurements of gamma radiation is examined. It is shown that if ionization chambers made of light-atom materials have walls less than 4.0 mm. thick, secondary beta radiation is recorded so that readings are in excess of the true values. The results explain some discrepancies found by other workers.

Further Studies Relating to the Implications of Radiation Survival Curve Data for Treatment of CBA Mouse Leukaemia by Whole-body Irradiation

Experiments are described which examine the effect of a single X-ray dose of 2000 r to the knee joint and tibia of six-week-old mice upon the uptake of 32P in these bones at varying intervals after irradiation up to 22 weeks. It is shown that in the knee joint, after a latent period of about one week the uptake of 32P falls progressively to reach a minimal value of about 55 per cent after about four weeks. The relationship of these results to those obtained by others for the depression of alkaline phosphatase activity is discussed. It is suggested that the time sequence of the irradiation effects involved may be suppression of osteoblastic activity leading to immediate and increasing depression of alkaline phosphatase activity as a result of which, after the latent period, new calcification is depressed in increasing amount until the maximum is reached. This depression is maintained until about eight to ten weeks after irradiation following which a slow recovery seems to occur, but this is still incomplet...

An account is given of the various physical factors of the new four-gramme radium unit at Westminster Hospital Annexe. The radiation fields available for treatment are described, and it is shown that the protection afforded is adequate, and better than that in the case of the previous two-gramme unit.

The results are given of a series of water phantom measurements, by Sievert's condenser chamber method, on the intensity distributions of the 2 gm. radium bomb in use at the Westminster Hospital Annexe, London. The best thickness of secondary copper filter is discussed and results are given that show “back-scatter” at the surface to be negligible for this particular unit. The results for the measurement of doses for various radium-skin distances are expressed graphically. The expression of therapeutic doses in r units is discussed, and the skin erythema dose in r, thus found, is compared with values given by other workers.

In 1940 Sievert published curves of the measured variation of γ-ray ionization with air pressure obtained with spherical elektron metal condenser chambers with smaller inter-electrode distances (0·25–0·50 mm). These showed that as the pressure was reduced, the ionization per cm of mercury, measured at atmospheric pressure, increased very rapidly instead of remaining constant at 100 per cent as it should according to the Bragg-Gray theory of cavity ionization. A calculated curve obtained by Sievert (1940) showed that ionization by collision did not entirely account for his observations. In Fig. 1 Sievert's curves have been replotted to show the relation between observed current and pressure of air, the current per cm of mercury measured at atmospheric pressure being taken as 100. The curves are straight lines which we have extrapolated back to zero pressure. In effect, some current is still present at zero pressure when theory indicates zero current, and this for very low chamber potentials. Sievert's calc...

The Effect of Tissue Oxygen Tension on the Radiosensitivity of Leukaemia Cells Irradiated In Situ in the Livers of Leukaemic Mice

Measurements with an extrapolation ionization chamber are described which aim to measure the ionization within chambers with high Z walls when the chamber dimensions are extrapolated to zero. The extrapolated values of ionization per unit volume are compared with those calculated from the Bragg-Gray theory. They agree well with the theoretical values for elements at least up to Z = 13 (Al) for radiations up to 0·5A. For elements of greater Z and for λ above about 0·10A, agreement is not found between the experimental results and the original theory. Better agreement can be obtained if the theory is modified so as to take into account the fact that in the ejection of the photoelectrons from the K shell of the wall material, an appreciable proportion of photon energy is used. The significance of these results is discussed from the point of view of measuring the energy absorbed in media.

The results of treatment of cerebral tumours by radiotherapy are generally admitted to be very unsatisfactory, although recently Peirce, Cone, Elvidge, and Tye (14) report rather more hopeful results. We have little knowledge of what types of cerebral tumour, if any, are suitable for radiotherapy (Bailey, 4; Bailey, Sosman, and Van Dessel, 5; Alpers and Pancoast, 1; Tarlov, 21). There is a good deal of evidence, also, that doses of x-rays or gamma rays likely to be effective in destroying a tumour have a destructive effect on brain tissue (Fischer and Holfelder, 8; Lyman, Kupalov, and Scholz, 11; Scholz, 17 and 18; Scholz and Hsu, 19; Markiewicz, 12; Wachowski and Chenault, 22), as well as on the skull (Camp and Moreton, 7). It seemed, therefore, that it would be useful to investigate the effects of radiation on experimental cerebral tumours in animals. Part I The production of cerebral tumours by the introduction of carcinogens into the brain tissue of experimental animals is not an entirely simple matte...