Document 6wn85KGBEYdpXdEy3d1YB0ZGd

zh an antu pered andI ig is fuset intil, as it about 'Its and e plates -eatment -trengthitructure re than l-bearing neet speuser as table. VOLUME TWENTY-TWO 1958 NUMBER THREE ting High"*? I AINT: RED- | rr.p^6 aints includtnc i ntended appli- painted, lhf I jriven. and the . -cd. Reprinted Maintenance.' FRY CORFO i for the peirf>; . How to avofi | red with leadin detail. Rf` April. 1938. sD TLASHI** . he new 2\'3 \ >i detailed draalog." 1958. toilead pipe f today** ind' e tailed drawinT J weet'a Caul* N V. *. * COMfaitY. iitic errr Over 20 tons of lead are included in the shield of the "Modified Swimming Pool" research reactor at the Naval Research Laboratory, Washington, D. C. See story page 7. LIA 26148 Lead Superconducting Connections Fig. 1. top. Specially prepared Aircraft Marine Products tapered plug. The film is on the straight wire. The crooked wire is the external lead. The crimping tool head is above the plug. Fig. 2, bottom. Completed compressed lead powder connection. An o t h er case where lead's fabrica- is soldered to the tapered end, and - bility and one or more of its in the whole is covered with a surface trinsic properties have been employedcoating of solder. The film-coated in solving a problem is exemplified wire is inserted into the hole at the by International Business Machine end of the plug, the cavity is filled Corp.'s utilization of lead's supercon with lead powder and a crimper is ductivity (the transition temperature used to compact the lead in an amount for zone refined lead is 7.175 0.005 determined by eye after a few trials. deg. K in zero magnetic field). As Figures 1 and 2. first reported by researcher J. A. The second method is easier to Kurtz in a recent issue of IBM Jour apply than the first and reduces the nal, lead for making superconducting strain by supporting the wire on the connections to thin films of vapor- plastic base. A small amount of pow deposited metal in cryogenic circuits dered lead is put into the cavities at has been found useful. the ends of the block and the film- Because the resistance of the cir coated wire is inserted in the slots. cuits immersed in liquid helium must Solder-coated copper wires are also be exactly zero, compressed lead put into each cavity through the same powder of the smallest commercial slots, whereupon the cavities are filled particle size is used as an interme with lead powder. A punch is used to diate superconducting contact between compact the lead under a pressure of the film and external circuitry. In about 5,000 psi, Figures 3, 4, and 5. making such contacts, two methods For the intended application, the were tried, the first making use of a current at which the self-field transi specially prepared plug, and the sec tion out of the superconducting state ond, supporting the wire on a plastic takes place is determined by passing base which remains permanently at successively greater known currents tached to the sample. Of the two through the test specimens. Switching methods tried for affixing the solder- is taken as destruction of the super covered wire to the film-covered wire, conducting state resulting from the the second was better. critical self field. The appearance of In the first method, the film coating voltage across a specimen, as detected is easily damaged by flexing the un by a voltmeter with 10 microvolt full supported wire. (A fractured film scale sensitivity serves to identify the would give a lower critical current.) onset of the transition. In it the prongs of the plug are Contacts made to vapor deposited flattened down, a solder-covered wire tin films by the first method have car- 2-- -- LIA26149 d, and urface coated at the filled iper is imount trials, ier to :es the on the if powities at e film: slots, e also e same e filled used to sure of and 5. in, the transig state massing ur rents itching superim the ince of etected olt full ifv the / posited ve car L | [ | k [ [ j [ ; | f i| ; i i V ried up to 200 ma. at a temperature of 3.67 deg. K without switching. Contacts made by the second method to similar tin films carried up to 1.25 amp. at 3.67 deg. K. Lead's normally high resistivity coupled with the superconducting transition has made lead and certain lead alloys attractive in other applica tion areas as well, in flip-flop circuits, gates, counters and other computer circuitry. In summary, the advan tages of lead in superconducting (or crvogenic) circuits are: 1. It has a high critical field so that it does not switch into the nor mal state by self-field when a gate strip of tin switches. 2. It is readily available in the purity and type (granules, powders, bars, etc.) desired and is not too expensive. 3. It vaporizes easilv so that flat film cryotrons can be made up by METHODS FOR MAKING LEAD SUPERCONDUCTING CONNECTIONS Modified AMP tapar plug for compressing lead powder. Plastic base and metal punch for com pressing lead powder. vacuum evaporation techniques. 4. When used in powder form to make the connections described, no heat is required and only moderate pressure need be used. Full exploitation of superconductive phenomena is yet to be had but star tling developments are in the offing. Investigations are now being made into alloying and the effects of hydro static pressure on lead's transition to the superconducting state. Another Record-Breaking Bridge Printed With Red Lead Paint TVie Quinnipiac River Bridge at A New Haven, Conn., with its central three-span continuous plate-girder unit. is the largest structure on the 129 mile half-billion dollar Connecti cut Turnpike. Two of the span lengths are 258 ft. with a center span nf 3117 ft., the longest for this type of ctiii'iruction in the Western Hemi'plicrc. This record-breaking bridge, carry ing six lanes of Turnpike traffic is nine-tenths of a mile long. Included in this distance are the three-span continuous unit. 903 ft. long, 2.541 ft. of simple-span girders varying from 125 to 175 ft. in span length and 1,290 ft. of simple-beam spans varying in length from 57 to 93 ft. In addition, the west end of the struc ture is widened at two locations to accommodate ramp structures of sim ple-beam construction. At the east abutment, the roadway is widened to 120 ft. to provide access and exit ramps to city streets. This bridge joins with another rec ord breaker, the Mackinac Bridge (Lead. Volume 21, No. 21 in the selection and use of red lead paint to plastic TABLE I SPECIFICATION for I'KIMER AND FIRST HELD COAT i.H INMPIAC RIVER BRIDGE AND INTERCHANGE I'lunient: Per Cent by Wt. Hi-il lead (95% grade) 75.0 min. Kill Iron Oxide (80% fe.O, min.) 25.0 max. Win, ir: I m, initiated Linseed Oil One:, and Turpentine 100.0 95.2 min. 4.8 max. 1 '-inirnt I per rent bv ' \ '"urle Iper rent bv ' " la'u pergallon (lb.) lime (hours to in through) 100.0 73.5-75.5 24.5-26.5 22.0 24 max. The steel work of the Quinnipiac River Bridge and triple interchange, called a "can of worms ' by the contractors, has two coats of rust-inhibiting red lead paint. LIA26150 protect the structural steel against corrosion. Both of these outstanding bridges were designed in the offices of D. B. Steinman, consulting engi neer of New York. The formulation for the red lead paint used on the Quinnipiac Bridge for the primer and first field coat appears in the accompanying table. A "can of worms" is what the con tractors have so aptly named the triple interchange located within downtown Xew Haven, see accom panying photograph. The eastbound and westbound roadways within this interchange are at different levels and as much as 350 ft. apart to provide necessary underclearance and suffi cient space for multitudinous road ways. The total length of paved road- An engineer's rendering of the completed Quinnipiac Bridge, the largest struc ture on the 129-mile Con necticut Turnpike, and at right, during construction. AU steel received nvo coats of red lead paint. way within the 1.48 miles of this particular part of the Connecticut Turnpike is 5.36 miles, of which 2.19 miles are on steel structures that have been protected against corrosion by a primer and field coat of lead paint, Bethlehem Steel Co. fabricated the steel work and R. M. Boynton, associate engineer with D. B. Steinman. was in charge of the project. Lead -- The Standard In Stereophonic Sound n e of the latest and most exciting The Clevite Corporation produces O new uses for lead is in the field a variety of lead zirconate-titanate of stereophonic sound. Two leadmaterials, known to the trade as zirconate-titanate elements comprise PZT," for these cartridges and for the heart of a new series of pickup other purposes. These elements are cartridges capable of transforming the able to transform record groove vibra vibrations in the groove of a stereo tions into sound through the unique phonic record into the wonder of property of piezoelectricity or "pres stereophonic sound. sure electricity." Since the nineteenth century, piezoelectric materials have been known to have the ability to generate electricity when subjected to stress or pressure. Some crystals have this property in their natural state, some ceramics can be given this property by electrical polariza tion. Conversely, they will elastically deform independently under the in- Temperature dependent properties "PZT' vs. barium titanate LI A26151 Iluence of an electric field. Lead zirconate-titanate is one of the perform Cutaway of PZT Stereophonic Cartridge ance leaders in this field. Stereophonic sound, the exciting new major step in the hi-fi world, re quires two separate channels of Lead zirconate-titanate Channel element, left sound. A unique design of the cutting and playback cartridge has made it Single stylus possible to combine these two chan nels on a single record, with a single stylus--hi-fi parlance for needle--in a single groove. The sound channels are picked up and fed separately to the ears to yield the impression of 3- dimensional sound, or a true feeling of "presence ". The stylus transmits vibrations picked up from the record tiroove to two separate "PZT" ele ments, as shown in the accompanying Lead zirconate-titanate figures. Each element is oriented so Channel element, right as to be sensitive to motion in only one direction. The elements are placed in the cartridge so that their polarities are at 90c angles to each other. In effect, two channels can be recorded into one groove with each Drawing and diagrammatic sketch showing location of lead zirconate-titanate ele ments on a stereophonic cartridge. biwuiwai signal tv amplifier and speaker amplifier and speaker element picking up only the motion in the direction to which it is sensi tive. The superior properties of "PZT" Record grooves Diamond stylus transmits vibrations to PZT elements above which make it so desirable for a stereophonic pickup are principally its higher electromechanical coupling materials. Basically, this is again due --its electrical output to mechanical to its higher electromechanical coup input, and its lower modulus of elas ling and also to its higher Curie tem ticity. A lower modulus of elasticity perature. The Curie temperatures of results in a pick-up element of higher "PZT" materials can range up to compliance or flexibility. These fea 300 C. which compares with a Curie tures are desirable because of the temperature of 110 C. for barium greater complexity and delicacy of titanate. The result is that not only the pickup system. The stylus in a can these materials be used at sub stereophonic pickup cartridge has a stantially higher temperatures, but sharper point than in a standard they can be driven to higher mechani playback cartridge. Therefore, in cal power outputs at lower ambient order not to cause excessive record temperatures without incurring any wear, it is necessary to reduce the loss of power when the temperature of forces between the stylus and the the transducer rises during operation. record groove. The higher compliance An exciting future is seen for this and greater electrical output of these material. It has already found a new lead zirconate-titanate elements makes use as a transducer material for our it possible to reduce these forces and Navy's sonar underwater detection yet still obtain a good electrical signal vequipment. Moreover, "PZT" electro from the cartridge. mechanical filter devices called Piezoelectric materials have been "Transfilters"* have been designed known for many years. They form the by Clevite which can take the place basis of the fields of ultrasonic flaw of the intermediate frequency trans detection, ultrasonic cleaning, etc. In formers in radio circuits. Other uses general, the use of "PZT" greatly in in this field are envisaged. This high creases the reliability and operating * Reg. U.S. Pat. Off. range of devices presently using other by Clevite Corp. power output material may very well find a big market for itself in the field of ultrasonic cleaning. There may come a day when the average housewife will have a dishwasher which owes its excellent cleaning powers to lead zirconate-titanate transducers. JUST PUBLISHED RED LEAD TECHNICAL LETTER NO. 13. A SINGLE RED LEAD PRIMER FOR RUSTED. WEATH ERED OR NEW GALVANIZED STEEL This primer has proved itself after 6 years of field exposures and re search work. It will effectively protect galvanized surfaces against further deterioration regardless of their condition. LEAD AND ITS ALLOYS. A re print from the September, 1958, issue of "Industrial and Engineering Chemistry." The annual review of new technical developments in lead, its alloys and compounds with a comprehensive bibliography. Roth of the above are available from the Association upon request. 5-- -- |_I A2615Z ti r ~*i i * r -- rt-rt i fin-**1 ---THE DOYLE SCRUBBER This cage-constructed Doyle Scrubber is treating gases from crusher and conveyor transfer points for dust recovery at Cominco's smelter feed and sinter plant at Trail, B.C. Over 4,900 lb. of antimonial lead sheet, from 24 lb. at the bottom to 8 lb. on sides above water line are used in. the scrubber. An operational detail is shown at right. New Lead-Constructed Scrubber In Use An ew wet-impingement scrubber undergoes a complete reversal of di has been developed by The Con rection, leaving the impingement tank solidated Mining and Smelting Coma t the top, then entering the spray pany of Canada Limited as a more elimination section. The clean gas is efficient recovery unit for the treat subsequently exhausted or used in ment of dusts and fumes from process other processes. gases and ventilating systems. Known as the Doyle Scrubber, it utilizes prin ciples of wet-impingement collection at relatively high gas velocities with high recovery efficiency and low in stallation and maintenance costs. As indicated in the sketch, the gas stream, laden with fume and dust, enters the downcomer duct, where upon its velocity is increased by the annular gap provided by the place ment of a streamlined cone at the duct bottom. Desired impingement veloci ties are obtained by use of cones of appropriate base diameters or, if a wide variation in gas volume is antici Cominco has over 20 lead-con structed Doyle Scrubbers in use to treat exhaust gases from materials transfer points in its metallurgical plants to eliminate atmospheric dust. These scrubbers are of lead-on-steelcage construction which contributes to low-cost installation and mainte nance. Advantages provided by this mode of construction are: 1. Effective performance of lead in contact with variable concentrations of a wide variety of corrosive process gases and solutions. pated, with an adjustable cone. The 2. Repair is made possible from impure gas, after entering the liquid the outside. 3. Where the chamber design calls for extra support for the lead lining, this can be provided externally, with the avoidance of internal strapping and the necessity for piercing the sheets. 4. Lower material and erection costs and easier construction through the elimination of unwieldlv steel sheets. 5. Easy leak detection. When steel chambers are lined with lead, it is customary to provide "weep holes" to indicate the development of leaks. However, corrosives do not always follow a detectable path from the point of failure to the weep hole and observed leaks are often merely an indication of their occurrence rather than of location. The cage construc tion, on the other hand, permits im mediate location of any leak and easy accessibility for repair. The Doyle Scrubber has been made available by Cominco to industry gen erally through licensed manufacturers. Power: Scrubbing Liquid: Table 1 Operating Requirements for Lead-Lined Doyle Scrubber 2.2 to 3.0 hp./l,000 c.f.m. of gas 2 gal. water/1,000 cu. ft. of gas. In some applications,, the rate is as low as 0.5 gaL/1,000 cu. ft. of gas---discharged to settling tanks for recovery of solids. Liquid is returned to scrubbing system. Impingement Velocities: 90 to 240 ft./sec., usually 15(1 ft/sec. I Inlet gas volume: 6,000 c.f.m. at 30 C. 1 Inlet dust burden: 140 to 180 mg. percu. ft. Outlet dust burden: 0.1 mg. per cu. ft. Draft across scrubber: 10 inches w.g. j ij | LIA26153 1 Lead Shield In Naval fit tune rues fit 'HUH" retr/tti toutssi f seerft* // tutHTt rsfitsi Ctiut '***** ` Nuclear Reactor Menunutttf eat cttrtti u* stem ttts OSS/U CSSMtft at cutset tit! flCUiili PUS v er 20 tons of lead has been in O cluded in the shield of the "Modified Swimming Pool" research an cuts sum teneast tturnit* tun ett reactor at the Naval Research Labora tory in Washington, D. C. This re actor and its associated facilities have been designed to meet the needs of a wide variety of investigations in the physical sciences. Its principal func iO'SSUti tic as' it/ttifi rm stance csi're t/rt itliCttT a rut sfcnu tion is to provide an intense source of neutrons and gamma rays required in many aspects of the laboratory's research programs. Access to neutrons and gamma rays is provided by seven beam ports which penetrate the con crete and lead shield right to the core of the reactor. These radiations are extremely useful as a research tool in the fields of nuclear physics, solid state physics, metallurgy, chemistry, mechanics, electronics, and reactor technology. A Modified Swimming Pool reactor with beam ports was chosen because of its flexibility in dealing with varied research problems. The presence of the pool allows the reactor to be used to study radiation shielding design problems of nuclear reactors for ship propulsion and electric power genera tion. The pool is 40' long x 26' wide x 2012' deep and contains high purity water in order to minimize corrosion of the reactor core and to obviate the possibility of activation of water im purities. This water provides part of the radiation shielding for the re actor ; it serves as a coolant to remove the heat formed in the uranium core and; finally, it is a moderator slowing down fast moving neutrons in the core to thermal energies. One end of the pool consists of a heavy lead and concrete radiation shield including several beam ports with removable plugs. It was neces sary to keep the shield thickness to a minimum so that the beam ports 'could be as short as possible. In order to accomplish this, a shield utilizing lead in conjunction with heavy aggre gate concretes was designed. Because of lead's high density, it provides efficient shielding against gamma : easier ;t n-temtes turf; CUCtei tut iSSi rust iim. A cutaway of the "Modified Swimming Poof re search reactor at the Naval Research Laboratory. radiation. The use of lead will sub stantially reduce the thickness of ma terial required to accomplish a given amount of shielding. Due to the re quirements of a compact shield in this reactor, the use of lead was a natural choice. The shielding consists of several layers. Immediately outside the ura nium core is a layer of carbon blocks whose excellent ability to scatter high energy neutrons makes it useful as a neutron reflector. Surrounding the carbons blocks is a lead brick shield which has been designed to absorb much of the gamma radiation from the core. The lead is followed by heavy barytes concrete which is a strong neutron absorber. The final layer of the shield consists of a con crete containing iron ore and iron punchings which serves as additional gamma ray shielding. Lead performs an additional significant function in this shield. It absorbs a portion of the gamma ray energy and fast neu tron energy entering the shield. By absorbing this energy, the tempera ture in the concrete shield is mini mized. In this way, the moisture con tent of the concrete, which is of major importance in neutron energy degra dation, is not driven off. Lead is widely considered in the field of nuclear energy as one of the basic shielding materials. In addition to its use in reactors and portable radiographic equipment where com pactness is desired, lead is widely used around atomic laboratories in a variety of experimental applications, in hospitals and, in general, wherever there is a necessity for shielding against gamma rays. Lead Water Closet Connections r at t Housing in Brooklyn, N. Y,, ceived practically universal accept Pa Title I, F.H.A. Slum Clearance ance by the building fraternity and Project, and a dormitory building athere are a number of excellent rea the Manhattanville College of the sons why this is so. Sacred Heart, Purchase, N. Y., are First, lead connections are flexible two recent examples of the widespread enough to permit allowances for slight acceptance of lead water closet con inaccuracies in construction measure nections for all types of construction. ments, an advantage that can result in Whether it be for these types of substantial savings when the fixtures construction, for single-family homes are set in place. Secondly, lead is or for commercial-type buildings durable, it will not corrode and rust flexible lead connections have re- out under normal operating use. --7-- LIA26154 Flexible lead bends as shown above were installed under more than 1,000 water closets in Pratt Houses, an F.H.A. Title I project under construction at right. At left, lead bends for wall-waste water closets in the Manhattanville College dormitory. Purchase, ;V. Y. Finally, lead connections are accept able to all modern day plumbing codes including those that are na tional in scope. Among such codes is the National Plumbing Code which was sponsored by the American Pub lic Health Association and the Amer ican Society of Mechanical Engineers. In the Manhattanville College Dor mitory Building, flexible lead bends and stubs roughed through the walls were used for the 80 wall-waste, floorset water closets. The plumbing con tractor, Hauxwell and Smith, PortChester, N. Y., also installed 20 6-lb. sheet lead roof drains and 12 4-lb. sheet lead vent stack flashings. The architects were Eggers & Higgins, New York, and Jarros, Baum and Bolles were the mechanical engineers. In the much larger Pratt Housing project in Brooklyn, N. Y., more than 1,000 lead water closet connec tions will be installed in three 16story reinforced concrete structures. The buildings will have 18 apart ments with 23 water closets on each floor. This moderate priced F.H.A. Title I project was designed by Kess ler & Sons, architects of New York, and the extensive plumbing system was installed by Lipsky & Rosenthal of Brooklyn, N. Y. t h f /Wt j r r a r y of Technical Information The following article* and reprint* contain information, drawings and specifications on the use of lead produets helpful to architects, engineers and others interested. They are available free of eharge except where otherwise indicated, upon request to the LEAD INDUSTRIES ASSOCIATION, 60 East 42nd STREET, NEW YORK 17, N. Y. MATERIALS OF CONSTRUCTION ANNUAL REVIEWS--LEAD AND LEAD ALLOYS Lead and lead alloys in design and construction including research progress, engineering applica tions, and technological advancements. With bib liography. 1957 and 1956 reviews (editions are not cumulative) are available. Reprinted from "Indus trial and Engineering Chemistry,'* September, 1957 ,:mi September, 1956. BEST DESIGNS FOR LEAD INSTALLATIONS A special report on the applications of lead and lead alloys in the chemical and metallurgical in dustries. Recommended practice for joining lead sheeta, and the construction of wood stave tanks, launders, towers and flues where lead is involved are included. Reprinted from "Chemical Engineer ing." March, April and May, 1956. USE LEAD TO CONTROL REFINERY CORRO SION Latest practices in lead construction for the petro leum refining industry are described. How to avoid the difficulties sometime* experienced with leadlined equipment is also outlined in detail. Re printed from "Petroleum Refiner," April, 1958. RADIATION PROTECTION The place of lead in shielding against radiation in X-ray and atomic energy applications. Principles of lead shielding construction. Reprinted from "Lead In Modern Industry." PORTABLE RADIATION. SHEILDING MATERIALS A special report on commercially available shield ing forms that can be used to build readily as sembled, band stacked shielding walls. Prepared by the editors of "Nucleonics," May. 1955. LEAD WORK FOR MODERN PLUMBING $1.50 Postpaid, $1.00 per eopy in quanti ties of 10 or more Profusely illustrated with over 140 photographs and drawings, the textbook presents clearly to the plumbing student the necessary tools, procedures and the methods required for lead work. LEAD IN MODERN INDUSTRY $1.00 Postpaid A fully illustrated, 230 page, cloth bound book describing all phases of the production and use of lead, lead alloys and lead compounds. LEAD BUILDING CONSTRUCTION BULLETINS A series of specifications for the use of lead ia building construction. (Available separately.) BULLETIN NO. 1 Specification for Lead Waste Connections for Plumbing Fixtures with Integral Traps (Water Closets--Pedestal Urinals--Service Sinks), BULLETIN NO. 2 Specification for Lead Shower and Safe Pans. BULLETIN NO. 3 Specification for Lead Chemical Laboratory Drainage Systems. FEDERAL SPECIFICATION WW-P-32S For Pipe, Bends and Trapsi Lead Dimensions and weights of lead products used in the plumbing and water works fields are given. Published by the Government Printing Office. LEAD WELDING An informative as well as practical guide to lead welding. Reprinted from the "Welding Handbook, Third Edition" published by the American Welding Society. LEAD FLASHINGS IN MODERN CONSTRUC TION Lead flashings as used in an ultramodern house in Randolph, Vt. Reprinted from "National Roofer." October, 1954. SHEET LEAD FOR ROOFING AND FLASHING Preferred installation methods for the new 2Vj and 3-lb. hard lead are given along with detailed draw ings. Reprinted from "Sweet's Catalog," 1953. LEAD FOR MODERN PLUMBING Preferred installation methods for lead pipe and fittings in the plumbing systems of today's indus trial and residential structures. Detailed drawings are included. Reprinted from "Sweet's Catalog,'* 1958. THE STORY OF LEAD--MATERIALS THE RAILROADS BUY (Parts 1 and 2) Lead from mine to finished product with special reference to its uses by the railroads. Reprinted from "Railway Purchases and Stores," December. 1954 and February, 1955. RED LEAD TECHNICAL LETTERS A series of technical letters containing red lead paint formulations. (Available separately.) Technical Letter No. 11 -- Recommended Surface Preparation of Steel for Red Lead Paints. Technical Letter No. 12--Painting Highway Structural Steel. FEDERAL SPECIFICATION FOR PAINT: RED- LEAD-BASE, READY-MIXED TT.P-86a Covers four types of red-lead-base paints including two fast drying formulations. Many intended appli cations listed. PAINT GALVANIZED SURFACES? Why galvaaixed surfaces should be painted, the kind of pretreatment that should be given, and the correct painting systems are discussed. Reprinted from "Factory Management and Maintenance," April, 1956. UPON REQUEST, THE LEAD INDUSTRIES ASSOCIATION WILL BE CLAD TO MAIL "LEAD" REGULARLY, FREE OF CHARGE, TO THOSE INTERESTED, AND WILL COOPERATE WITHOUT OBLIGATION IN THE SOLUTION OF YOUR LEAD PROBLEMS. HUNTED t> l'. K. *** IsVAC COLDMANN IXVtslO* PESLISKERA PRINTING--ROGERS KELLOGG COUP l o n c in l an d errr 1. n . r. LIA26155 T I