IOSR-JAP   Volume-6 ~ Issue-3 ~ May-June 2014

Paper Type	:	Research Paper
Title	:	Formation of Potassium Nanostructures on Reconstructed High Index Si (5512)2x1 Surface for Night Vision Devices (NVD)
Country	:	India
Authors	:	Awanish Kumar Sharma, Manoj Dhiman, Ram Kumar, Sulaxna Sharma (Dr.)
	:	10.9790/4861-06320108

ABSTRACT: In the present study potassium nanostructure was grown on the high index reconstructed Si (5512) 2x1 surface due to their potential application in the night vision devices (NVD). The formation of potassium atoms (K) on high index Si semiconductor under controlled kinetic and thermodynamic growth conditions having desired shape and size with low work function were studied. The studies have been performed on a reconstructed high index silicon surface at room temperature as well as on high substrate temperatures such as (375, 550 and 680 ºC). The structural properties of the high index trenched template have been exploited for the development of desired nanostructures of different size and shape. It is constructed to a planner surface having a single domain with 1-D symmetry and relatively largest unit cell (5.35 nm). In the present study, growth of potassium nanostructures on the high index reconstructed Si (5 5 12) surface occur, which can be potentially utilized in night vision devices. The experiments were performed in-situ in a Ultra high vacuum (UHV) system in-housed with various surface sensitive techniques such as Auger Electron Spectroscopy (AES), Electron Energy Loss Spectroscopy (EELS), and Low Energy Electron Diffraction (LEED).
Key Words: High index Si Surface, Potassium metal, Night Vision Device

[1]. M. K. Govind,, V. K. Palival, S.M. Shivaprasad; Vacuum 82 (2008) 1452-1456.
[2]. H.H. Song, K.M. Jones, A.A. Baski; J. Vac. Sci. Technol. A 1696 (1999)171.
[3]. J. N. Crain, A. Kirakosian, K. N. Altmann, C. Bromberger, S. C. Erwin, J. L. Mcchesney, J. -L. Lin, F. J. Himpsel; Phys. Rev. Lett. 90 (2003) 176805.
[4]. S.R. Blankenship, H.H. Song, A.A. Baski, J.A. Carlisle; J. Vac Sci Technol A 1615 (1999) 17.
[5]. J.W. Dickinson, J.C. Moore, A.A. Baaski; Surf. Sci.561 (2004)193.
[6]. J.R. Ahn, H.W. Yeom, E.S. Cho, C.Y. Park; Phys. Rev. B 69 (2004) 233311.
[7]. S.S. Lee, N.D. Kim, C.G. Hwang, H.J. Song, J.W. Chung; Phys. Rev. B 66 (2002) 115317.
[8]. P.H. Woodworth, J.C. Moore, A.A. Baski; J. Vac. Sci. Technol. A 21 (2003) 1332.

Paper Type	:	Research Paper
Title	:	Optical properties of pulse electrodeposited ZnS films
Country	:	India
Authors	:	K. R. Murali
	:	10.9790/4861-06320914

ABSTRACT: ZnS films were deposited by the pulse plating technique at different duty cycles in the range of 6 – 50 % and at a constant current density of 10 mA cm-2.. The films exhibited single phase hexagonal ZnS. The grain size increased with decrease of duty cycle. Optical band gap of the films increased from 3.83 – 4.01 eV with increase of duty cycle. Optical constants (refractive index, n, extinction co-efficient, k, dielectric constant) of the films were obtained in the wavelength range 300-1850 nm by using spectrophotometric measurement. The obtained results concerning the absorption index yield the energy gap in addition to the type of the allowed optical transitions. N/m* ratio has been obtained from refractive index data. The dispersion of refractive index is analyzed by using a single oscillator model.
Keywords: electrodeposition, electronic materials, optical properties, semiconductors, thin films

[1]. R.Maity and K.K.Chattopadhyay, Synthesis and optical characterization of ZnS and ZnS:Mn nanocrystalline thin films by chemical route, Nanotechnology, 15(7), 2004, 812 - 816.
[2]. Y.T.Nien, I.G.Chen, C.S.Hwang and S.Y.Chu, Copper concentration dependence odf structure, morphology and optical properties of ZnS:Cu,Cl phosphor powder, J.Phys.Chem.Solids, 69 (2-3 ), 2008, 366.- 371
[3]. T.Nakada, K.Furumi,andA.Kunioka, High efficiency cadmium free CuIInGa)Se2 thin film solar cells with chemically deposited ZnS buffer layers, IEEE Trans.Electron.Devices, 46 (10), 1999, 2093 - 2097
[4]. A.Fujii, H.Wada, K.I.Shibata, S.Nakayama, M.Hasegawa,In:R.W.Tustison (Ed.), Window and DomeTechnologies and Materials VII,SPIE,Bellingham, 2001, p206.
[5]. F.Gὂde and C.Gumus, Influences of copper and manganese concentrations on the properties of polycrystalline ZnS:Cu and ZnS:Mn thin films, Optoelectron. Adv. Mat.11 (3 ), 2009, 429 - 436.

Paper Type	:	Research Paper
Title	:	The influence of Calcium doping on structural and electrical properties of ferroelectric Lead Titanate ceramic
Country	:	India
Authors	:	Nagarbawadi M. A., Jangade P. S., Bagwan S. T
	:	10.9790/4861-06321519

ABSTRACT: A series of Lead Titanate ceramic with various concentration of Calcium has been prepared by solid state reaction method, and some of their physical properties and structural characteristics have been studied. The incorporation of small amount of Calcium results in considerable changes in the dc electrical conductivity and the temperature of the ferroelectric phase transition. Lead Titanate (PT) is a well known ferroelectric with high curie point and low dielectric thus constant making it an attractive proportion for various applications. The synthesis of Calcium modified PbTiO3 was carried using solid state reaction method. Stoichiometric amount of high purity CaO was used as a dopant in different proportion and the final product was in powder form. The X-ray diffraction pattern was taken for pure and CaO modified Lead Titanate. The SEM of the sample was done on JEOL 6360A Analytical Scanning Electron Microscope. There is an observable change in grain size with different molar concentration of Calcium oxide. The DC conductivity of the sample was carried out using two probe method over a range of temperature covering their transition temperature.
Keywords: Curie temperature, CaO, DC conductivity, PbTiO3 , SEM

[1]. J. Valasek, Phys. Rev. 17 (1921) 475.
[2]. A.Ahmed, K.Besso, S.Chehab,T.A.Wheat. J. Mater.Sci.25(1990),5289-5302.
[3]. A.J. Moulson and J.M. Herbert, Electro ceramics, Chapman and Hall, 1990, U.K
[4]. Pontes F.M, Pontes D.S.L,Leite E.R & Longo E ,J.Appl.Phys 94 (2003).7256.
[5]. Chauhan A K S,Gupta V & Sreenivas K,Mater Sci Engg,B 130(2006) 81.
[6]. T. Yamamoto, M.Saho, K. Okazaki, and E. Goo, Jap. J. Appl. Phys., 26-2, 57 (1987)
[7]. K. M. Rittenmyer, and R. Y. Ting, Ferroelectrics, 110, 171 (1990)

Paper Type	:	Research Paper
Title	:	Simulation of photovoltaic (PV) power system performance of spacecraft in geostationary orbit using a prototype model
Country	:	Nigeria
Authors	:	Muhammad Dokko Zubairu , Ekundayo O. Ajala
	:	10.9790/4861-06322026

ABSTRACT: The most important system on-board any spacecraft is its electrical power system, as every other subsystem requires power to operate. Photovoltaic (PV) array meets the total power requirements of the spacecraft in the geostationary orbit during its entire mission life. PV array consists of number of solar panel substrates on which solar cells are laid down in series and parallel for its power requirement generation. This paper presents the effects of varying temperature and irradiance on the solar energy generation based on the fundamental circuit equations of a solar PV cell model. Thus, an increase in irradiance at constant temperature, the voltage and current output also increase. Whereas, at constant irradiance, an increase in temperature decreases the power output from PV array. The model produces various curves for I-V and P-V characteristics of the PV array.

Keywords: Spacecraft, Mission life, Photovoltaic array, Solar cell, Simulink

[1]. CAST, "Nigcomsat-1R Satellite Technical Data," S.C Centre, Ed., ed. Abuja 2011.
[2]. Jervase, J.A., Bourdoucen, H., and Al-Lawati, A., "Solar cell parameters extraction using genetic algorithm,' Journal of Measurement Science and Technology, Vol.12, 2001, pp.1922-1925.
[3]. Nelson J., "The Physics of Solar Cells," 1st Edition, ed. Imperial College Press, 2005.
[4]. Patel M.R., "Spacecraft Power Systems," CRC Press, 2005.
[5]. Rauschenbusch H.S., "Solar Cell Array Design Handbook," JPL SP 43 – 38, vol.1, Van Nostrand Solar, 1980.
[6]. Sharma S.K., Pavithra D., Srinivasamurthy N. and Agrawal B.L., "Determination of Solar cell parameters: an analytical approach," Journal of Physics D: Applied Physics, Vol.26, No.7, 1993, pp.1130-1133.

Paper Type	:	Research Paper
Title	:	Full energy peak efficiency calibration and efficiency transfer to ETNA in Gamma Ray Spectrometry
Country	:	Bangladesh
Authors	:	Subrata Banik, Saudia Jannat Satyajit Ghose , M Islam , S M Azharul Islam
	:	10.9790/4861-06322733

ABSTRACT: Accurate determination of the radionuclide concentration in environmental sample depends directly on the accurate efficiency calibration in gamma ray spectrometry. The detection efficiency may vary due to some factors (density, sample filling height, matrix, measurement geometry, self-absorption, detection system, etc.) for voluminous samples. Some studies has been conducted in this work and presented in here. The efficiency calibration was performed for two HPGe detectors (relative efficiency of 20% and 40%), using samples (STDMS, STDMP, STDMPF, STDMRL, STDB, STDMC, & STDMG) of various densities (0.55 to 1.59 g/cm3) in cylindrical containers (V=240 cm3) for the gamma ray energy range of 121 keV to 2614 keV. Secondary reference material was prepared by using the standard reference liquid source 152Eu. From the experimental result it can be seen that efficiency value is inversely proportional to the gamma ray energy. For lower gamma energies of selected nuclide, the efficiency value comparatively higher than the high energies of that nuclide. Efficiency value also varies with filling height of sample. Computer software ETNA was used for the efficiency transfer measurements of three samples (STDMP, STDMPF, & STDMRL) for the configuration of 20% relative efficiency detector. The efficiency value obtained from ETNA was compared with analytical efficiency value. Approximately 2.2% to 15.5% variation was found within the two systems. From the result it can be said that at the initial stage this kind of technical approach is not convenient for the environmental sample measuring laboratory due to the availability of input data for running the ETNA.
Keywords: Efficiency Calibration, ETNA, Gamma-Ray Spectrometry, HPGe Detector

[1] Jun Saegusa, Katsuya Kawasaki, Akira Mihara, Mitsuo Ito, Makoto Yoshida, Determination of detection efficiency curves of HPGe detectors on radioactivity measurement of volume shapes, Applied Radiation and Isotopes; 61 (2004); 1383-1390.
[2] G. Hasse, D. Tait and A. Wiechen, Determination of full energy peak efficiency for cylindrical volume sources by the use of a point source standard in gamma spectrometry, Nuclear Instruments and Methods in Physics Research A, 361 (1995, 240-244.
[3] J. P. Pérez-Moreno, E. G. San Miguel, J.P. Boliıvar, J. L. Aguado, A comprehensive calibration method of Ge detectors for low-level gamma-spectrometry measurements, Nuclear Instruments and Methods in Physics Research A, 491 (2002), 152–162.
[4] Z. B. Alfassi, N. Lavi, The dependence of the counting efficiency of Marinelli beakers for environmental samples on the density of the samples, Applied Radiation and Isotopes, 63 (2005), 87–92.
[5] International Atomic Energy Agency, A Guidebook on Measurement of Radionuclides in Food and the Environment, Technical Reports Series No. 295, Vienna, 1989.

Paper Type	:	Research Paper
Title	:	Modeling Of Sokoto Cement Production Process Using Finite Automata: Compact Model
Country	:	Nigeria
Authors	:	Z. Ibrahim, A. A. Ibrahim, I. A. Garba , D. M. Sahabi
	:	10.9790/4861-06323437

ABSTRACT: Automata models are among the computational models used in design and construction of industrial processes. Deterministic finite automata are used for specific operation procedures involving known start and specific accepting and or end states. This paper adopts the method of the deterministic finite automata to construct the compact production model by using the production processes to denote different states linked by different transition functions. The preliminary results indicate that from the compact model of the cement production processes the transition table so obtained can be used to interpret the order of the cement production process and a gateway towards studying more detailed transition matrix in terms of algebraic theoretic properties.
Key Words: Finite State Machine, States, Automata and Transitions

[1] AhoA. Y. and Ullman J. D. (1995), Foundation of Computer Science (C Edition), Computer Science Press.
[2] Cement Company of Northern Nigeria Plc. (2012). Quality Control Information Desk
[3] Garcia-Diaz A. and Lee H. (1995),An Industrial Application of Network-flow Models in Cellular Manufacturing Planning. Planning, Design, and Analysis of Cellular manufacturing System Elsevier Science.
[4] Hopcroft J. E., Motwani R., and Ullman J. D. (2001), Introduction to Automata Theory, Languages and computation (2nd Edition), Addison-Wesley.
[5] http://en.wikipedia.org,25th December 2013

Paper Type	:	Research Paper
Title	:	The Dependence of Spatial Distribution of Excitement of Receptors on Their Stiles-Crawford Effect
Country	:	India
Authors	:	Nachieketa K Sharma
	:	10.9790/4861-06323841

ABSTRACT: The spatial distribution of excitement of receptors depends on the magnitude of amplitude of light integrated over the wavefront passing through the pupil as conditioned by the receptor's acceptance lobe. Because the peripheral zones of the pupil are less efficient in eliciting visual excitation than the pupil's centre, otherwise known as Stiles-Crawford effect of the first kind (SCE I), the spatial distribution of excitement of receptors will differ depending on their Stiles- Crawford effect. Assuming the funneling of light into the receptors through a single entering aperture the SCE I is integrated into the calculation of retinal diffraction images, in the manner of an apodization effect. And, in the absence of aberrations, the pupil apodization is chosen twice as narrow as suggested by the SCE I to compute modulation in the retinal light distributions. But using coherent illumination, a periodic target of rectangular profile and incorporating SCE I as pupil apodization we got a result where neither the intensity nor the modulation changes indicating absence of SCE I for a full pupil admitting a single coherent beam.
Keywords: Stiles-Crawford effect, Coherent illumination, Apodization, Rectangular grating.

[1]. W. S. Stiles and B. H. Crawford, "The Luminous Efficiency of Rays Entering the Pupil at Different Points," Proc. Roy. Soc. B, 112, 428-450 (1933).
[2]. P. Jacquinot, P. Bougron, and B. Dossier, "Calcul et realisation des distributions d'amplitude pupillaire, permettant a suppression des franges laterale dans les figures de diffraction," in La Theorie des Images Optiques, P. Fleury, A. Marechal, and C. Anglade, eds. (Editions de la Revue d'Optique, 1949), pp. 183-193.
[3]. L. J. Bour and J. C. M. Verhoosel, "Directional Sensitivity of Photoreceptors for Different Degrees of Coherence and Direction of Polarization of the Incident Light," Vis. Res. 19, 717-719 (1979)
[4]. B. Vohnsen and D. Rativa, "Absence of an Integrated Stiles-Crawford Function for Coherent Light," Journal of Vision, 19, 1-10 (2011)
[5]. S. Castillo, and B. Vohnsen, "Exploring the SCE-I with Coherent Light and Dual Maxwellian Sources," Appl. Optics 52, A1-A8 (2013).

Paper Type	:	Research Paper
Title	:	A Dosimetric study of different MLC expansion aperture For the radiotherapy of pancreas cancer
Country	:	Egypt
Authors	:	Mohammad F. Hassan, Mahmoud A. Hefni, Mohamed El-Azab Farid , Khaled M. Elshahat
	:	10.9790/4861-06324254

ABSTRACT:Radiotherapy is using of ionizing radiation in the treatment of cancer. The aim of radiotherapy is to annihilate the tumor tissue while minimizing damage to the normal surrounding tissues. We can do that by using shielding like custom blocks and MLCs. Uses the MLCs now in all the sites, but does not use blocks except in the necessity of it, as there are different types of MLCs in thickness (1 cm and 0.5 cm, and finally 0.3 cm). The MLCs are not limited to the use of three-dimensional planning only, but also using in the most modern techniques like IMRT and IGRT. When shaping the radiotherapy treatment field size of the tumor, there are some concepts must be included in the accounts, such as the concept of penumbra and radiotherapy field size and the impact of change that field size on the dose distribution within the tumor and dose receiving by OARs. When the field size is shaped where the MLCs ends are attached with tumor (the MLCs margin = 0.0 cm) the penumbra effects on the tumor cover percentage, so the distance between tumor and MLCs ends (MLC margins) must be existing to overcome the penumbra effects. To determine the most adequate MLC margins which achieve the tumor dose coverage a many plans with difference MLC margins were compared from 0.0 cm to 1.2 cm the comparison included the tumor coverage percentage and the received dose to OARs and if it under tolerance or not. After that we can selection the best MLC margins to work out in most famous techniques for pancreas cases. Results: the tumor is not cover when the MLC margins less than 0.5 cm, and from MLC margins 0.5 cm to 0.7 cm the tumor is cover very well and OARs are under tolerance, the MLC margins more than 0.7 cm the tumor cover is very well but OARs received unnecessary doses. After 1.2 cm MLC margin, the saturation occurs of the tumor cover percentage. Conclusions: The best MLC expansion apertures for the radiotherapy of pancreas cancer are from 0.5 cm to 0.7 cm.

[1]. Khan, Faiz M.(2010) Physics of Radiation Therapy, The, 4th Edition: Lippincott Williams & Wilkins.
[2]. Murat Beyzadeoglu , Gokhan Ozyigit , Cuneyt Ebruli (2010) Basic Radiation Oncology: Springer-Verlag Berlin Heidelberg 2010.
[3]. Podgorsak EB (2005) Radiation oncology physics: a handbook for teachers and students. International Atomic Energy Agency, Vienna.
[4]. Podgoršak E (2007) Radiation physics for medical physicists, 1st edn. Springer, Berlin.
[5]. Cormack DV, Johns HE. Spectral distribution of scattered radiation from a kilocurie cobalt 60 unit. Br J Radiol. 1958.
[6]. Pam Cherry MSc TDCR, Angela M. Duxbury MSc FCR TDCR (2009) Practical radiotherapy: physics and equipment – 2nd Ed. This edition first published 2009.

Paper Type	:	Research Paper
Title	:	On the Homotopy analysis method of MSEIR epidemic model
Country	:	Nigeria
Authors	:	M.O. Ibrahim ,I.I. Raji, A. Aladesuyi , A.Nwagwo
	:	10.9790/4861-06325561

ABSTRACT: We considered an MSEIR epidemic model as proposed by Hethcote (2000). Homotopy analysis method is used to solve the problem because of its advantages over methods.
Keywords: Epidemic, Homotopy

[1].A.A.M. Arafa, S.Z. Ridaand M. Khalil, (2012). Solutions of fractional or dermodel of childhooddiseaseswithconstantvaccinationstrategy, MathematicalSciences,Letter 1(1),17-23.
[2]. E.O.Ifidon,(2009)anApplication ofHomotopyAnalysistotheViscousFlow Past aCircularCylinder. J.Appl. Math. 1-17.
[3]. F.Awawdeh,A.AdawiandZ.Mustapha,(2009).SolutionsoftheSIRmodels of epidemicsusingHAM,Chaos,SolitonsandFractals, 42,3047- 3052.
[4]. G.A.NgwaandW.Shu,(2000).A Mathematicalmodelforendemicmalariawith variable humanand mosquito populations, Mathematicaland Computer Modeling32:747-763.
[5]. G.Shabbir, Hikhanand M.A.Sadiq,(2010).AnoteonExact SolutionofSIR AndSISepidemicmodels,arXiv:1012.5035,20-25.
[6]. H.W.Hethcote, (2000).TheMathematicsofInfectiousDiseases,SIAMReview 42(4):599-653.
[7]. L.Yajie,B.T. Nohara,andS.J. Liao,(2010). SeriessolutionsofcoupledVan- derPolequation bymeans ofhomotopyanalysis method, JournalofMathematicalPhysics51:1-12.

Paper Type	:	Research Paper
Title	:	Cosmic Ray Breakdown Mechanism in the Atmophere
Country	:	Nigeria
Authors	:	Akande, P. I, Azi Amaechi O., A. O. Chikwendu, Nwoba Isreal A.
	:	10.9790/4861-06326264

ABSTRACT: Cosmic rays are high energy particles originating from outer space. These cosmic rays produce secondary cosmic rays as they enter the atmosphere and generate runaway electrons. The generation of runaway electrons in the relativistic region of the atmosphere is the focus of this work. To achieve our aim, basic consideration is given to the cold electron having mean velocity which is less than electron thermal speed. The effects of force on these electrons are obtained. From the result, it shows that cosmic ray breakdown occurs in the atmosphere within the relativistic region and the electrons are accelerated by the electric field. Hence there is an exponential increase of the fast electrons. This exponential increase in fast electron in the atmosphere could be the basic reason for the spontanouse characteristic behavour of most atmospheric processes.

[1]. Aleksandr, V., Gurevich, A. N., Vladimir, A. R., Aleksandr, P. C. and Aleksandr, L. S. (2009). Non-linear Phenomena in the Ionospheric Plasma: Effects of Cosmic Rays and Runaway Breakdown on Thunderstorm Discharges. Ann Geophys, 24, 529-542.
[2]. Apel, W.D and Arteage J.C,(2011). Thunderstorm observations by air-shower radio antenna arrays. Advances in space Research (a cospar publication). Vol.48, pp 1295-1303.
[3]. Devendra Simgh and Singh R.P, (2010). The role of cosmic rays in the Earth's atmospheric processes. Centre for sun-climate Research, Danish National space Institute copehagen, Denmark. Vol. 74. Pp 153. 168.
[4]. Ermakov, V.I., Kokin, G.A., Komotskov, A.V., Sorokin,M.G., (1992). Results of measurements of the concentrationof negative ions in the polar stratosphere. Geomagnetismand Aeronomy 32 (3), 47.
[5]. Gurevich, A.V; Milikh G.M; and Roussel Dupre R. (1992).Runaway electron mechanism of air breakdown and preconditioning during a thunderstorms, physics letters A, vol. 165,468.

Paper Type	:	Research Paper
Title	:	Influence of ventilation conditions on the radon annual effective dose of the lungsimulatedfor radon prone areas of Ramsar
Country	:	Iran
Authors	:	Mehdipour L.A, DoostMohammadi F, Saion EB, Qasemi N, Hadavi M
	:	10.9790/4861-06326570

ABSTRACT: Ramsar of northern Iran located on the littoral of the Caspian Sea is considered one of the radon prone areas of the world. The annual effective dose in the district of Talesh-Mahalleh is higher than the dose limits for radiation workers by at least 13 times. In the present study, the indoor radon concentration and radon annual effective dose of the lung were estimated using a Prassi portable radon gas survey meter in a ventilated model house containing top soil samples from different parts of Ramsar. The average wind speed was maintained at 3.0 ms-1 matching the average wind speed of the region. For the extremely hot samples, the annual effective dose of the lung was 111±10.20mSv y-1 when the windows closed. However, when the windows opened in the wind direction and in the opposite wind direction, the annual effective doses of the lung were 2.46±0.86 and 4.16±0.81mSvy-1, respectively. Also, when the crossed windows opened in no wind condition, the radon annual effective dose of the lung was 5.43±0.86mSvy-1. The results suggest by opening the windows a significant reduction of the radon annual effective dose in buildings of Ramsar can be achieved.
Key words: radon gas, annual effective dose, natural ventilation, Ramsar

[1]. Kendal GM, Smith TJ, Doses to organs and tissues from radon and its decay products. Radiat Prot, 2002, 22(4), 389-406.
[2]. WHO. hand book on indoor radon Diagnostic measurements for mitigation and post-mitigation. 2009.
[3]. Ghiassi-nejad M, Mortazavi SMJ, Cameron JR, Niroomand-rad A, Karam PA, Very high background radiation areas of Ramsar, Iran: preliminary biological studies. Health Phys. 2002; 82(1):87-93.
[4]. Sajo-Bohus L, Palfalvi J, Urbani F, Castro D, Greaves ED, Liendo JA. Environmental gamma and radon dosimetry in Venezuela. Radiat measurment, 1999, 31(1–6), 283-286.
[5]. Jönsson, G. Radon gas - where from and what to do? Radiat measu, 1995, 25(1–4), 537-546.
[6]. Barros-Dios JM, Alberto RR, Monica PR. Residential Radon Exposure, Histologic Types, and Lung Cancer Risk. A Case–Control Study in Galicia, Spain. Cancer epid, Bio and prev, 2012; 21(6),951-958.