Direct detection of maize in pottery residues via compound specific stable carbon isotope analysis.

Direct detection of maize in pottery residues via compound specific stable carbon isotope analysis. Introduction Maize was domesticated do��mes��ti��cate?tr.v. do��mes��ti��cat��ed, do��mes��ti��cat��ing, do��mes��ti��cates1. To cause to feel comfortable at home; make domestic.2. To adopt or make fit for domestic use or life.3. a. in the Valley of Mexico The Valley of Mexico is a highlands plateau in central Mexico roughly coterminous with the present-day Distrito Federal and the eastern half of the State of Mexico. Surrounded by mountains and volcanoes, the Valley of Mexico was a center for several pre-Columbian civilizations, , and became animportant part of North American North Americannamed after North America.North American blastomycosissee North American blastomycosis.North American cattle ticksee boophilusannulatus. diets around 1000 cal AD (Doebley, J.1990; Van der Merwe & Vogel 1978; Vogel & van der Merwe 1977).By the time of European Contact (c. 1500 AD) maize was the primarystaple food in North America, comprising up to 90 per cent of the dietof some native cultures (Broida 1984; Larsen 2000; Lynott et al. 1986;van der Merwe & Vogel 1978; Wagner 1986). The rapid adoption of thisproductive crop has been demonstrated by stable carbon isotope analysisof human skeletal remains. Since maize is a [C.sub.4] tropical grass,its [[delta].sup.13]C value is distinctively more positive than the[C.sub.3] temperate grasses that dominate the ecosystem of North Americaeast of the Great Plains (Buikstra & Milner 1991; Lambert et al.1979; Larsen et al. 1992; Lynott et al. 1986; van der Merwe & Vogel1978; Vogel & van der Merwe 1977). Such isotopic differences arepassed up the food chain and may be detected in human skeletal remains.Stable carbon isotope analysis demonstrated that extensive maizeadoption was contemporaneous with dramatic increases in population,social stratification, and urbanisation in North America (Buikstra etal. 1987; Fritz 1992; Kelly 1992; Rindos & Johannessen 1991; van derMerwe & Vogel 1978; Voigt 1986). However, direct detection of maize in the pottery in which it wascooked permits study of how maize was processed, what other foodstuffs foodstuffsnpl → comestibles mplfoodstuffsnpl → denr��es fpl alimentairesfoodstuffsfood npl → it was processed with, and which parts of the population were cookingthe most maize, when and where. Such detailed examples in context shouldhelp to determine how or why this dietary shift occurred. Directdetection of maize in pottery can be accomplished by targetingcompounds, e.g. lipids, which are characteristic of maize and have thepotential to survive as components of organic residues absorbed into thefabric of pottery vessels. Absorbed organic residues Absorbed organic residues comprise complex mixtures of compoundsreleased from foods or other organic commodities processed in vessels,which become absorbed within the walls of ceramic vessels during thecooking process. As such, they are potentially valuable sources ofinformation on ancient diet. Once compounds are absorbed within thewalls various physicochemical processes preserve the lipids for manymillennia (Evershed 1993; Evershed & Charters 1995; Evershed et al.1999; Evershed et al. 1992a; Evershed et al. 1992b; Evershed et al.1990; Heron & Evershed 1993; Heron et al. 1989). The compounds thatsurvive can be extracted from potsherds and identified through gaschromatography/mass spectrometry (GC/MS GC/MS Gas Chromatograph/Mass SpectrometerGC/MS Gas Chromatograph/Mass SpectrometryGC/MS Gas Chromatograph/Mass Spectrograph ). Interpretation of residue compositions Interpretation of lipids that originate from complex mixtures ofancient foodstuffs is problematic. Correlation of fatty acid fatty acid,any of the organic carboxylic acids present in fats and oils as esters of glycerol. Molecular weights of fatty acids vary over a wide range. The carbon skeleton of any fatty acid is unbranched. Some fatty acids are saturated, i.e. compositionwas the first method used to identify contents of ancient vessels(Condamin & Formenti 1978; Condamin et al. 1976). This approach maybe valid in some cases, but fatty acid compositions do not provide agenerally applicable method of residue interpretation for two reasons.Firstly, most ceramic vessels would have contained more than onefoodstuff during their use-life; the fatty acid compositions of suchmixtures can combine to mimic the composition of a single food that wasnot present in the residue. Secondly, unsaturated and short-chain fattyacids degrade more quickly during deposition and burial than saturated,long-chain fatty acids, thus changing fatty acid compositions over time(Dudd & Evershed 1998, Reber & Evershed 2004). Althoughdegradation can be modelled (Malainey et al. 1999; Malainey et al.2001), environmental variations between sites are such that fatty acidratios can be used to determine only generalised categories, such asprimarily meat or primarily plant/fish. The fatty acid composition ofmaize is largely limited to oleic acid oleic acid/ole��ic ac��id/ (o-le��ik) a monounsaturated 18-carbon fatty acid found in most animal fats and vegetable oils; used in pharmacy as an emulsifier and to assist absorption of some drugs by the skin. ([C.sub.18:1]), linoleic acid linoleic acid/lin��o��le��ic ac��id/ (lin?o-le��ik) a polyunsaturated fatty acid, occurring as a major constituent of many vegetable oils; it is used in the biosynthesis of prostaglandins and cell membranes. ([C.sub.18:2]), stearic acid stearic acid/ste��a��ric ac��id/ (ste-ar��ik) a saturated 18-carbon fatty acid occurring in most fats and oils, particularly of tropical plants and land animals; used pharmaceutically as a tablet and capsule lubricant and as an emulsifying ([C.sub.18:0]), and palmitic acid palmitic acid/pal��mit��ic ac��id/ (pal-mit��ik) a 16-carbon saturated fatty acid found in most fats and oils, particularly associated with stearic acid; one of the most prevalent saturated fatty acids in body lipids. ([C.sub.16:0]), all extremely common fatty acids present in almost everyknown foodstuff. Thus, maize cannot be directly detected through fattyacid composition alone. The second method of residue interpretation is a biomarker approachbased on other diagnostic lipids. This approach is enhanced by thedetermination of compound-specific stable isotope values for individualbiomarker compounds. This technique has been used to detect dairy fats(Copley et al. 2003; Dudd & Evershed 1998), to determine thepyrolytic py��rol��y��sis?n.Decomposition or transformation of a compound caused by heat.pyro��lyt origins of certain long-chain ketones (Evershed et al. 1995),to identify the presence of waxes from vegetables of the genus Brassica(Evershed et al. 1999), to identify degraded beeswax beeswax:see wax. beeswaxCommercially useful wax secreted by worker honeybees to make the cell walls of the honeycomb. A bee consumes an estimated 6–10 lbs (3–4. in Aegean lamps(Evershed et al. 2003; Evershed et al. 1999; Evershed et al. 1997), andto distinguish ruminant ruminant,any of a group of hooved mammals that chew their cud, i.e., that regurgitate and chew again food that has already been swallowed. Ruminants have an even number of toes on each foot and a stomach with either three or four chambers. from non-ruminant animal fats (Dudd et al. 1999;Evershed et al. 2002; Mottram et al. 1999). Compound-specific isotopeanalysis of residues is performed using the gaschromatograph-combustion-isotope ratio mass spectrometer (GC-C-IRMS).This instrument allows isotopic analysis of compounds separated from amixture. Since an absorbed residue may contain compounds from diversesources, GC-C-IRMS is an appropriate tool for determining the isotoperatios of different foodstuffs that contributed to components thatcomprise a residue. Compound-specific stable isotope analysis and the detection ofmaize Given the distinctive [[delta].sup.13]C value of maize (a [C.sub.4]plant) in the predominately [C.sub.3] ecosystem of North America,compound-specific isotope analysis is an obvious choice for directdetection of maize lipids absorbed in archaeological pottery from NorthAmerica. Since maize is the most common [C.sub.4] plant eaten inEastern/Midwestern North America, and the only domesticated [C.sub.4]plant in that region, a plant compound with a [C.sub.4] signature couldonly reasonably derive from maize. This likelihood can be raised tonear-certainty if the compound measured is abundant in maize but rare inmost other plants. We have identified n-dotriacontanol as a compoundthat fits this description remarkably well (Bianchi et al. 1984;Gunstone et al. 1994). Archaeological samples In order to explore the compound-specific stable isotope analysisof n-dotriacontanol as a method of directly detecting maize residues inarchaeological pottery, 130 potsherds from 16 sites along theMississippi Valley were submitted to organic residue analysis. Sampleswere chosen by temporal and geographic provenance, in an attempt toobtain a progression from pre- to post-maize-growing societies. Fourgeographical clusters of sites provided separate temporal progressions.Maize was adopted very late in the Lower Mississippi Valley, whilepeople in the American Bottom region adopted the crop early anddeveloped the earliest urban culture in Midwestern North America. Thepeoples of the Illinois River Valley probably cultivated maizeextensively only after its acceptance in the American Bottom (c. 1000cal AD), while the Wisconsin River Valley is located in the northernlimits of maize agriculture. Samples were obtained from both recentarchaeological excavations and from museum collections. All sherdsshowed evidence of use for processing plant and/or animal products overa fire, due to the presence of extensive carbonised deposits or externalsooting. Since maize was a staple crop after about 1000 cal AD in theAmerican Bottom, and slightly later in the Illinois and Wisconsin RiverValleys, it seemed reasonable to assume that at least some pots wouldhave been used to cook maize. Exploration of n-dotriacontanol as a maize marker in organicresidues The primary stumbling block in the detection of maize products inresidues is the slow uptake of maize lipids into pottery. Maize kernelsare composed on average of 71.7 per cent starch, 9.5 per cent protein,and only 4.3 per cent lipid (Watson & Ramstad 1987). Uptake of maizelipids into pottery is probably less significant than for oily or fattyplant or animal foodstuffs which contain much higher concentrations oflipid. In order for common fatty acids to have a detectable isotopicsignature a large amount of maize would have to be cooked in a vesselrelative to high lipid content [C.sub.3] foodstuffs. Although plantsterols make up a higher percentage of maize lipids than usual for agrain, sterols make up only 5 per cent of kernel lipids (Watson &Ramstad 1987). Likewise, a large amount of maize would have to beprocessed in a vessel before detectable quantities of plant sterolswould become absorbed into the ceramic wall. Previous studies of organicresidues in pottery vessels, however, suggest that sterols do notpreserve well during deposition and burial (Aillaud 2001; Reber 2001). The long-chain "alcohol, n-dotriacontanol, however has thepotential to serve as a biomarker for maize with a characteristic stableisotope value. This compound almost certainly originates in plant waxes(Kolattukudy 1976; Walton 1990) and although present in low abundancesin many plants, it is abundant in panicoid grasses, such as maize. It isa common constituent of maize wax, making up 29 per cent of freealcohols in maize kernel waxes, and 15 per cent of alcohols in waxesters (Bianchi et al. 1984). n-Dotriacontanol is especially importantbecause processing maize and non-maize plants together will result inmixing between [C.sub.4] components from maize and [C.sub.3] componentsfrom non-maize plants. Such mixing will mask the [C.sub.4] signature ofmaize in many common compounds. Since n-dotriacontanol is relativelyrare in North American non-maize plants, however, such masking is highlyunlikely to occur in [[delta].sup.13]C values of n-dotriacontanol.Figure 1 illustrates [[delta].sup.13]C values of long-chain alcohols ina single residue from the Mees-Nochta site in the American Bottomregion. Commonly occurring compounds such as fatty acids are heavilymasked, and the [C.sub.4] signal of maize is not visible. Only the[[delta].sup.13]C value of n-dotriacontanol reveals the presence ofmaize products in the residue. A major advantage of n-dotriacontanol asan isotopically characteristic biomarker for maize is its excellentpreservation potential. Shorter-chain alcohols and other functionalisedcompounds tend to be more water-soluble and hence more likely to leachfrom pottery during burial (Eglinton & Logan 1991), while long-chaincompounds are less likely to be leached from pottery during burial.Furthermore, long-chain alcohols are unlikely to form during pre- andpost-depositional chemical reactions. [FIGURE 1 OMITTED] Long-chain alcohols were identified in both total lipid extractsand neutral fractions of the archaeological pottery, although chainlengths varied between the two fractions. Table 1 summarises thedistributions of long-chain alcohols detected in the free form and boundin wax esters of samples with a [C.sub.4] component. In general, morevessels contained esterified long-chain alcohols than free long-chainalcohols, and in higher abundances. This implies that alcohols of chainlengths [C.sub.30]-[C.sub.34] were primarily preserved as components ofwax esters; as mentioned above, n-dotriacontanol is the most abundantlong-chain esterified alcohol in maize. Furthermore, experimentaldegradation studies of maize lipids confirmed that the relativeabundance of n-dotriacontanol in absorbed organic residues increasesdramatically after only 3-6 months of burial due to the preferentialdecay of the more abundant acyl ac��yln.A organic radical having the general formula RCO, derived from the removal of a hydroxyl group from an organic acid.acyl1. an organic radical derived from a fatty acid by removal of the hydroxyl group.2. lipids (Figure 2) (Reber & Evershed2004). [FIGURE 2 OMITTED] Absorbed organic residues in archaeological pottery vessels n-Dotriacontanol was detectable in 16 of the potsherds examined inthis study. GC-C-IRMS analysis of these neutral fractions confirms thatn-dotriacontanol possesses a [[delta].sup.13]C value characteristic forthe identification of maize processing in a vessel. Of the 16 extractscontaining identifiable amounts of n-dotriacontanol, 10 producedreliable [[delta].sup.13]C values when analysed by GC-C-IRMS, which arepresented in Figure 3. The group of vessels displaying a narrow range of[[delta].sup.13]C values between -19 [per thousand] and -21 [perthousand] suggests a purely or almost purely [C.sub.4] origin. A widerrange of values between 26 [per thousand] and -33 [per thousand]suggests a range from pure [C.sub.3] to a mixture of [C.sub.3] and[C.sub.4] plant contributions. Alternatively, the wider spread maysuggest a range of atmospheric conditions for the [C.sub.3] plants,leading to different plant isotope values depending upon the[[delta].sup.13]C value of the C[O.sub.2] surrounding the plants, suchas a forested environment (van der Merwe & Medina 1991). The tightgrouping around the [C.sub.4] range is consistent with the presence ofmaize processing in the vessels. As discussed above, the rarity of[C.sub.4] plants in the North American diet suggests that any [C.sub.4]stable carbon isotope signature in plant compounds is likely tooriginate from maize. Moreover, the rarity of n-dotriacontanol innon-panicoid grasses suggests a low likelihood of [C.sub.4]n-dotriacontanol originating from any source other than maize. Therelative rarity of both n-dotriacontanol and the ingestion ingestion/in��ges��tion/ (-chun) the taking of food, drugs, etc., into the body by mouth. in��ges��tionn.1. The act of taking food and drink into the body by the mouth.2. of CAM andnon-maize [C.sub.4] plants in Midwestern & Eastern North Americamake a false positive identification of maize an unlikely eventuality. Maize products were identified primarily in residues from theAmerican Bottom region, one of the earliest regions of intensive maizeproduction and consumption in North America (Figure 3). The presence ofmaize products in residues was also identified in a small number ofsherds from the Lower Mississippi Valley, where the richness ofavailable marine resources would have made maize a less important partof the diet than in the American Bottom (Fritz & Kidder 1993; Kidder1992). Sherds from the Illinois River Valley and the GottschallRockshelter in Wisconsin did not yield detectable n-dotriacontanol. [FIGURE 3 OMITTED] Conclusions Isotope analysis of the long-chain alcohol n-dotriacontanol inabsorbed organic residues provides a new means of detecting the presenceof maize residues in archaeological pottery from Eastern and MidwesternNorth America. Using this technique, we can begin to track maizeprocessing and concomitant culture changes as maize became anincreasingly important part of the diet of native peoples in NorthAmerica. This technique is especially effective in [C.sub.3]environments in which maize is the primary [C.sub.4] dietary plant.Whether isotope analysis of n-dotriacontanol will effectively detect thepresence of maize in primarily [C.sub.4] environments awaits furtherinvestigation of the long-chain alcohol content of common plant foods inthose areas. We anticipate that the relative rarity of n-dotriacontanol,which imparts a high degree of specificity to the isotope analysis ofthis compound, will allow its use in archaeological investigation ofregions outside of Eastern and Midwestern North America. Technical Note Lipid extraction Following the method largely outlined by Evershed et al. (1990),all equipment and glassware were solvent-washed prior to use in lipidextraction. Sherds were cleaned using a drill bit; a scalpel was used toscrape visible residues from the sherd prior to cleaning. Sherds werethen crushed to a fine powder, and a weighed amount (2-3 g) wastransferred to a vial. n-Tetratriacontane was added as an internalstandard for the purpose of quantification. Lipid was extracted from thepowdered sherd with chloroform/methanol (2:1 v/v solution, 10 ml) byultrasonication (2 x 20 min). After centrifugation CentrifugationA mechanical method of separating immiscible liquids or solids from liquids by the application of centrifugal force. This force can be very great, and separations which proceed slowly by gravity can be speeded up enormously in centrifugal and passing thesupernatant supernatant/su��per��na��tant/ (-na��tant) the liquid lying above a layer of precipitated insoluble material. supernatantthe liquid lying above a layer of precipitated insoluble material. through silica gel (220-440 mesh), the solvent wasevaporated to produce extracted lipid. Derivatisation and fractionation fractionation/frac��tion��a��tion/ (frak?shun-a��shun)1. in radiology, division of the total dose of radiation into small doses administered at intervals.2. An aliquot aliquot(al-ee-kwoh) adj. a definite fractional share, usually applied when dividing and distributing a dead person's estate or trust assets. (See: share) of the extract was derivatised usingN,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA BSTFA N,o-Bis (Trimethylsilyl)trifluoroacetamide (derivatization reagent)) with 1 per cent v/vtrimethylchlorosilane (TMCS TMCS Trimethylchlorosilane (derivatization reagent)TMCS Telecommunications Management & Control SubsystemTMCS Taylor Made Computer Solutions, Ltd. ). Depending on the presence of measurablecompounds in the derivatised total lipid extract, a further aliquot ofextracted lipid was separated into fatty acid and neutral fractions. Thelipid was saponified with 2 M sodium hydroxide/methanol solution andheated at 70-80[degrees]C (1 h), with intermittent stirring. Thesolution was cooled and extracted with n-hexane (3 x 2 nd) to produce aneutral fraction, which was evaporated and stored at 2-5[degrees]C;prior to analysis an aliquot of this fraction was treated with BSTFA asabove. Instrumental analysis All extracts were analysed by gas chromatography using a HewlettPackard 5890 GC with on-column injection. Total lipid extracts wereanalysed using a 15 m x 0.32 mm internal diameter fused silica capillarycolumn with DB1 stationary phase (0.1 [micro]m film), with a temperatureprogramming from 50-350[degrees]C after a 2 min hold followinginjection, and a 10 min final hold at 350[degrees]C. Neutral fractionswere analysed on the same column, or with a CP-Sil 5 column. GC/MS analysis used either a Caro Erba Mega Series GC interfaced toa Finnigan MAT 4500 MS operated in electron ionisation Noun 1. ionisation - the condition of being dissociated into ions (as by heat or radiation or chemical reaction or electrical discharge); "the ionization of a gas"ionization (EI) mode,scanning from m/z 50-700, or a Finnigan MAT TSQ TSQ Times SquareTSQ Toronto Slavic QuarterlyTSQ Temporary Status by QualificationTSQ Training Staff QualificationsTSQ Tall, Still, and Quiet (how to should stand at attention in military formations)TSQ Temporary Storage Queue 700 series MS with anautoinjecter. GC-C-IRMS analysis used a Varian GC attached to a Finnigan MATDelta S MS with a Finnigan MAT Mark I combustion interface or a FinniganMAT Delta-Plus XL mass spectrometer. A CP-Sil 5 column was utilised forneutral fraction analysis on this instrument. The temperature programapplied to neutral samples held at 40[degrees]C for 1 min followinginjection, ramped from 40-2000[degrees]C (10[degrees]C [min.sup.-1]),from 200-250[degrees]C (3[degrees]C [min.sup.-1]), and 250-300[degrees]C(10[degrees]C [min.sup.-1]) with a 5 min hold at the final temperature.Table 1. Comparison of abundances of free and esterifiedlong-chain alcohols in vessels identified as containinga maize component. Long-chain alcohols [Cn(rel. abun.)] OtherPotsherd compounds present; source Free EsterifiedHRL 97 [C.sub.28](67), [C.sub.22](44), [C.sub.24](49), [C.sub.30](100) [C.sub.26](47), [C.sub.28](81), [C.sub.30](96), [C.sub.32](100), [C.sub.34](6)HRL 98 [C.sub.28](100), [C.sub.24](26), [C.sub.26],(52), [C.sub.30](56) [C.sub.28](100), [C.sub.30](62), [C.sub.32](41)HRL 134 [C.sub.28](100), [C.sub.24](24), [C.sub.26](34), [C.sub.30](50) [C.sub.28](100), [C.sub.30](97), [C.sub.32],(1)HRL 135 Undetectable [C.sub.24](28), [C.sub.26](34), [C.sub.28](93), [C.sub.30](100), [C.sub.32](36)HRL 169 Undetectable [C.sub.24](71), [C.sub.26](80), [C.sub.28](100) [C.sub.30](98) [C.sub.32](95), [C.sub.34](23)HRL 170 [C.sub.26](38), C26(44), C28(100), [C.sub.28](100), [C.sub.32](26) [C.sub.30](10), [C.sub.32](22)HRL 208 [C.sub.28],(50), [C.sub.22](45), [C.sub.24](46), [C.sub.30],(41), [C.sub.26](43), [C.sub.28](59), [C.sub.32](100) [C.sub.30],(70),[C.sub.32](100) Long-chain alcohols [Cn(rel. abun.)] OtherPotsherd compounds present; sourceHRL 97 [C.sub.16-30, 18:1] even-chain fatty acids, cholesterol; maize, animal, plant resources presentHRL 98 [C.sub.14-28, 16:1, 18:1, 20:1] even-chain fatty acids; maize, plant or possibly /fish resourcesHRL 134 [C.sub.16-30, 16:1, 18:1] even-chain fatty acids; primarily maizeHRL 135 [C.sub.14-28, 16:2, 18:2, 18:1] even-chain fatty acids; acids; primarily maizeHRL 169 [C.sub.12-30] even-chain fatty acids; maize and other plant resources.HRL 170 [C.sub.14-30, 16:1, 18:1] even-chain fatty acids; maize and other plant resourcesHRL 208 [C.sub.14-30] even-chain fatty acids; maize and other plant or possibly/fish resources. Acknowledgements We thank Jim Carter and Andy Gledhill for help with instrumentalanalysis. The National Science Foundation supported this research withaward # BCS-9980294. The UK National Environment Research Council isthanked for mass spectrometry facilities. Dr John Hayes, of the WoodsHole Oceanographic Institute, made invaluable comments and suggestions.The contributors of sherds to this study, and their institutions,provided information as well as pottery: Dr John Kelly of WashingtonUniversity and the Central Mississippi Valley Archaeological ResearchInstitute; Dr Timothy Pauketat of the University of Illinois University of Illinois may refer to: University of Illinois at Urbana-Champaign (flagship campus) University of Illinois at Chicago University of Illinois at Springfield University of Illinois system It can also refer to: atUrbana-Champagne; Dr Mary Beth Trubitt of Northwestern University, theUniversity of Michigan (body, education) University of Michigan - A large cosmopolitan university in the Midwest USA. Over 50000 students are enrolled at the University of Michigan's three campuses. The students come from 50 states and over 100 foreign countries. , and Henderson State University Henderson State University is a four-year public university located in Arkadelphia, Arkansas and serves as Arkansas’s public liberal arts college. It is a member of the Council of Public Liberal Arts Colleges. ; Dr T.R. Kidderof Tulane University and Washington University at St. Louis; DrNathanael Heller of the Louisiana Division of Archaeology; the Centerfor American Archeology The Center for American Archeology, or CAA, is an independent non-profit 501(c)(3) research and education institution located along the banks of the Illinois River, in Kampsville, Illinois, USA. ; and Dr Robert Salzer of Beloit College. Themembers of the Bristol Organic Geochemistry Unit provided assistance andadvice, particularly Drs Ian Bull and Paul Chamberlain. References AILLAUD, S. 2001. 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Archaic An archer. (ed.), Lipids, Membranes and Aspects of Photobiology photobiology/pho��to��bi��ol��o��gy/ (-bi-ol��ah-je) the branch of biology dealing with the effect of light on organisms.photobiolog��icphotobiolog��ical pho��to��bi��ol��o��gyn. 4:105-158. London: Academic Press. WATSON, S.A. & P.E. RAMSTAD (ed.). 1987. Corn: Chemistry andTechnology. St. Paul: American Association of Cereal Chemists. Eleanora A. Reber, (1) Stephanie N. Dudd, (2) Nikolaas J. van derMerwe (3,4) & Richard P. Evershed (5) (1) Anthropology Program, UNC (Universal Naming Convention) A standard for identifying servers, printers and other resources in a network, which originated in the Unix community. A UNC path uses double slashes or backslashes to precede the name of the computer. Wilmington, 601 S. College Rd,Wilmington, NC 28403, (Email: rebere@uncwil.edu) (2) Waters Corporation, Atlas Park, Simonsway, Manchester, M22 5PP.United Kingdom (3) Archaeology Department, University of Cape Town Coordinates: “UCT” redirects here. For other uses, see UCT (disambiguation). , Private BagRondebosch 7700, South Africa (4) Departments of Anthropology and Earth and Planetary Sciences,Harvard University (5) Organic Geochemistry Unit. Biochemistry Research Center,University of Bristol, Cantock's Close, Bristol BS8 1TS UnitedKingdom (Email: r.p. evershed@bristol.ac.uk) Received: 4 February 2003, Accepted: 9 September 2003