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The influence of water deficits and drought on tree physiological processes, growth, and survival has been the focus of substantial research efforts and debate over the past decades, but there is still a need to quantitatively link finer scale mechanistic explanations of the influence of water status with the physiological responses of trees, particularly for those past the sapling stage. Hence, the objective of this study was to link accumulated water stress during the growing season to leaf physiological response mechanisms of Juglans nigra L. trees. Results showed that trees subjected to higher cumulative water stress had lower maximum light-saturated photosynthesis (Amax), initiated net photosynthesis at higher light levels (Ic), and displayed reduced effectiveness of CO2 fixation per photons absorbed (Qe) at the bottom and upper positions along the vertical canopy gradient. Results suggest that water stress integral (Sψ), a variable that takes into account accumulated water deficits, would be useful to help future research efforts aimed at investigating responses to drought in trees past the sapling stage.

We studied late-entry commercial thinning effects on growth, yield, and regeneration in a 48-year-old jack pine (Pinus banksiana Lamb.) stand. Applied thinning intensities were 27, 32, and 47% of merchantable basal area (BA) excluding skidding trails. After 15 years, mean diameter at breast height of surviving trees in the 47% BA removal increased by 4.9 cm (25%) compared to the unthinned control. The 47% BA removal also increased gross merchantable volume (GMV) tree−1 by 46% compared to the control. The 27% BA removal had twice as much GMV ha−1 compared to the 47% BA removal after 15 years. Moreover, cumulative GMV ha−1 was much higher in the 27% BA removal than in the unthinned control. The highest thinning intensity produced larger trees on average, while the lowest thinning intensity maximized volume production per hectare. Maintenance of acceptable growing stock throughout the 15-year period in the 27% BA removal could provide other ecosystem functions such as biodiversity enhancement or wildlife habitat by delaying senescence. Regeneration data showed that a shift in species composition occurred in the understory. After 15 years, the understory was dominated by black spruce (Picea mariana (Mill.) B.S.P.), white birch (Betula papyrifera Marsh.), and trembling aspen (Populus tremuloides Michx.). If regenerating jack pine is an objective after final overstory removal, additional efforts will be needed to re-establish this species.

While light is a primary driver of tree growth and development, other environmental variables are also essential, including water, nutrients, and temperature. Ecophysiological studies have helped to uncover mechanisms underlying these interactive processes, but such trials have been mainly conducted on seedlings, with relatively few dealing with trees past the sapling stage. We used environmental and ecophysiological data collected on 28 trees (age 14–20 years) across three study sites in Indiana, USA for several growing seasons to identify variables that drive diameter growth of plantation-grown hardwoods past the sapling stage under non-limiting light conditions. Results showed that water stress (as reflected in leaf water potential) had the greatest influence on growth; relative diameter growth of black walnut (Juglans nigra L.), northern red oak (Quercus rubra L.), and white oak (Quercus alba L.) was reduced with increasing water stress. Compared to previous studies carried out with seedlings, results provide some evidence to suggest that ecophysiological responses to water stress may differ between seedlings, juveniles, and mature trees of the same species. Relative diameter growth of black walnut and northern red oak increased with increasing soil or leaf nitrogen. We did not find relationships between relative diameter growth of white oak and nutrient variables. Overall, these results have important implications for reforestation and forest management efforts in light of climate change.

Compared to in situ measurements, net photosynthesis and stomatal conductance were reduced 3–6 min after leaf detachment in Quercus rubra and Quercus alba, and 9 min after leaf detachment in Juglans nigra. Collecting in situ gas-exchange measurements in canopies of mature trees is challenging, because the crown can be several meters above ground. Thus, we investigated the effect of detaching the leaf from the branch and time since detachment for three deciduous angiosperm species: black walnut (Juglans nigra), northern red oak (Quercus nigra), and white oak (Quercus alba). Results showed that net photosynthesis (A) was significantly reduced 3 min after leaf detachment in Quercus rubra, 6 min after leaf detachment in Q. alba, and 9 min after leaf detachment in J. nigra. Compared to the in situ measurement, a 72 ± 13% reduction (mean ± SE) in A occurred after 3 min in Q. rubra, a 74 ± 27% reduction in A occurred after 6 min in Q. alba, while a 41 ± 14% reduction in A occurred after 9 min in J. nigra. Furthermore, once the significant reduction in A occurred, it was maintained over the remaining time period for each species. Responses for stomatal conductance were similar to those of A. Results highlight the importance of measuring gas exchange in situ whenever possible. Otherwise, these results provide threshold time periods to carry out instantaneous gas-exchange measurements in the field for select hardwood species in which the canopy is difficult to access.

SummaryThe heterogeneous properties of dermal cell populations have been posited to contribute toward fibrotic, imperfect wound healing in mammals. Here we characterize an adult population of dermal fibroblasts that maintain an active Prrx1 enhancer which originally marked mesenchymal limb progenitors. In contrast to their abundance in limb development, postnatal Prrx1 enhancer-positive cells (Prrx1enh+) make up a small subset of adult dermal cells (∼0.2%) and reside mainly within dermal perivascular and hair follicle niches. Lineage tracing of adult Prrx1enh+ cells shows that they remain in their niches and in small number over a long period of time. Upon injury however, Prrx1enh+ cells readily migrate into the wound bed and amplify on average 16-fold beyond their uninjured numbers. Additionally, following wounding dermal Prrx1enh+ cells are found out of their dermal niches and contribute to subcutaneous tissue. Postnatal Prrx1enh+ cells are uniquely injury-responsive despite being a meager minority in the adult skin.

The heterogeneous properties of dermal cell populations have been posited to contribute toward fibrotic, imperfect wound healing in mammals. Here we characterize an adult population of dermal fibroblasts that maintain an active Prrx1 enhancer which originally marked mesenchymal limb progenitors. In contrast to their abundance in limb development, postnatal Prrx1 enhancer-positive cells (Prrx1enh+) make up a small subset of adult dermal cells (∼0.2%) and reside mainly within dermal perivascular and hair follicle niches. Lineage tracing of adult Prrx1enh+ cells shows that they remain in their niches and in small numbers over a long period of time. Upon injury however, Prrx1enh+ cells readily migrate into the wound bed and amplify, on average, 16-fold beyond their uninjured numbers. Additionally, following wounding dermal Prrx1enh+ cells are found out of their dermal niches and contribute to subcutaneous tissue. Postnatal Prrx1enh+ cells are uniquely injury-responsive despite being a meager minority in the adult skin., Summary: Dermal Prrx1-enhancer cells are injury-responsive fibroblasts. Prrx1enh+ cells readily migrate into the wound bed and amplify on average 16-fold beyond their uninjured numbers.

We used long-term data collected from 22 study sites in northern hardwood stands comprised of sugar maple ( Acer saccharum Marsh.), yellow birch ( Betula alleghaniensis Britt.), and American beech ( Fagus grandifolia Ehrh.) to establish relationships between sapling abundance and tree ingrowth. After 10 years, postharvest sapling density in the 6 cm diameter class (5.1–7.0 cm) showed linear relationships with ingrowth. Proportion of variation explained ( r 2 ) varied from 36% to 83% depending upon tree species and silvicultural treatment (partial cutting vs. uncut control). After 20 years, linear relationships were also established ( r 2 = 24–65%) between ingrowth and sapling density in the 2 cm diameter class (1.1–3.0 cm). From a wide pool of variables related to stand species composition, climate, physiography, and soil nutrients, postharvest sapling density was most strongly correlated to merchantable tree density ( r = 0.43–0.75). Sugar maple sapling density was also positively correlated with base saturation and calcium saturation of the B horizon ( r = 0.56 and 0.58). Over a 30-year period, the increase in American beech sapling basal area was substantial compared to mitigated increases found in sugar maple and yellow birch depending upon treatment. Our results provide useful information on integration of sapling data into forest management.

We established a long-term experiment in a temperate mixedwood stand to evaluate the effectiveness of silvicultural treatments in regenerating a mixed-species cohort while maintaining the dominance of conifers. Silvicultural treatments included clearcutting using careful logging around advanced growth (CLAAG), uniform shelterwood (US), group shelterwood with (GS-s) or without scarification (GS), and an uncut control (control). After 10 years, height and ground-line diameter growth responses of advanced balsam fir (Abies balsamea [L.] Mill.) regeneration were substantial in CLAAG and GS compared to the control, and intermediate in US. Growth responses were proportional to increases in canopy light transmittance resulting from harvest. Advanced balsam fir regeneration had low mortality (

The suitability of indirect impedance to accurately measure microbial growth in real food matrices was investigated. A variety of semi-solid and liquid food products were inoculated with Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Lactobacillus plantarum, Pseudomonas aeruginosa, Escherichia coli, Salmonella enteriditis, Candida tropicalis or Zygosaccharomyces rouxii and CO2 production was monitored using a conductimetric (Don Whitely R.A.B.I.T.) system. The majority (80%) of food and microbe combinations produced a detectable growth signal. The linearity of conductance responses in selected food products was investigated and a good correlation (R2 ≥ 0.84) was observed between inoculum levels and times to detection. Specific growth rate estimations from the data were sufficiently accurate for predictive modeling in some cases. This initial evaluation of the suitability of indirect impedance to generate microbial growth data in complex food matrices indicates significant potential for the technology as an alternative to plating methods.

The introduction of the fungal pathogen Cryphonectria parasitica (Murr.) Barr. decimated American chestnut ( Castanea dentata (Marsh.) Borkh.) throughout its native range in North America. A blight-resistant backcross hybrid form of American chestnut has been developed, and these backcross trees are likely to be incorporated into restoration programs in the near future. To help guide future afforestation efforts, this study examined juvenile (five growing seasons) morphological and physiological competitive aspects of American chestnut grown in a plantation setting with northern red oak ( Quercus rubra L.) and black cherry ( Prunus serotina Ehrh.) in Indiana, USA. Species were grown in seven possible species combinations including both monospecific and polyspecific combinations at three densities (1 × 1 m, 2 × 2 m, and 3 × 3 m). Despite an initial advantage in height, American chestnut exhibited the lowest relative height growth in the 2 × 2 and 3 × 3 m spacings, resulting in less total height compared to the other two species 5 years after planting. Relative height growth, as well as final absolute heights, were comparable among species in the 1 × 1 m spacing. Black cherry exhibited 2–3 times greater relative ground-line diameter (GLD) growth compared to oak and chestnut at all spacings. Linear regressions showed that growth was generally proportional to net photosynthesis ( A ) for all species. Increases in A likely resulted from increases in leaf nitrogen concentration. Chestnut exhibited lower A than cherry and oak in years 2 and 3, but no differences occurred in year 4. Additionally, chestnut had significantly higher predawn leaf water potential (leaf Ψ pd ) in year 4, reflecting greater drought stress in cherry and oak. While black cherry grew most aggressively, northern red oak and American chestnut performed acceptably, with high survival rates and moderate growth, especially in the 1 × 1 m spacing. American chestnut had the poorest stem form overall, but fared better in the 1 × 1 m spacing where the crown competition factor (CCF) was highest. Hence, an intermediate spacing between 1 × 1 and 2 × 2 m could optimize chestnut’s growth and stem form. Mixture effects may be attributed mainly to individual species growth characteristics rather than inter-specific interactions during this juvenile developmental stage.

We evaluated the effectiveness of the regular shelterwood system in mitigating water table rise and regenerating a new cohort while favoring red spruce ( Picea rubens Sarg.) in an 80-year-old, red spruce – balsam fir ( Abies balsamea (L.) Mill.) lowland site. We used an experimental design established in 1994, with four completely randomized blocks and five treatments (uncut control, low, moderate, and heavy shelterwood cuttings, and clearcutting). In 2006, final overstory removal was carried out in the three shelterwoods and we monitored the first five growing seasons after treatment. Results showed that final cut did not lead to significant watering-up during the 2006–2010 period compared to levels measured in 1999, but water table levels did not fully recover from shelterwood cutting or clearcutting compared to precut levels measured in 1994. Under conditions of abundant seed supply, poor drainage, and low herbaceous and noncommercial woody competition, clearcutting (0.25 ha patches) provided the best red spruce cohort in terms of regeneration density, stocking, and growth. Balsam fir and red maple ( Acer rubrum L.) regeneration was abundant in both silvicultural systems. Regeneration density and stocking of red spruce, balsam fir, and all commercial broadleaf species were generally lower inside logging trails than between trails, likely due to disturbance by machinery. For poorly-drained lowland sites, findings indicate patch clearcutting may be more effective in regenerating red spruce than the regular shelterwood system.

The resistance of an Enterobacter pulveris strain to combined heat and supercritical carbon dioxide (scCO 2 ) treatments in different powder matrices was examined. The strain proved resistant to scCO 2 treatment up to 50MPa pressure at temperatures >73°C for at least 20min in a commercial infant formula. Water availability was shown to be important for the observed thermotolerance, because introduction of water in the scCO 2 gas flow during treatment resulted in a 1 log 10 cfu/g reduction of the initial inoculum. Interestingly, similar tolerance to heat and scCO 2 treatment was observed in a less complex matrix, a maltodextrin powder. In contrast, the bacterial strain proved sensitive to lower temperatures (55–65°C) over shorter times (≤10min) in a dextrose powder composed of crystalline particles. Therefore, the microorganism demonstrates heat sensitivity in the crystalline powder matrix closer to that of nonpowder liquid matrices. These data demonstrate the increased heat tolerance of the bacterium specifically in amorphous powders and indicate that this characteristic is not dependent on fat and other components commonly found in infant formula. The information is important in designing strategies to deal with contamination of powders with Enterobacteriacae , including pathogenic Cronobacter spp.

We applied four precommercial thinning (PCT) intensities (unthinned control, 2.5, 3.0, and 3.5 m residual spacings) to aspen ( Populus tremuloides Michx.) stems, while preserving understory balsam fir ( Abies balsamea (L.) Mill.) in an even-aged stratified boreal mixedwood stand. We evaluated treatment influence on aspen and balsam fir growth, and regeneration dynamics over a 10-year period. Compared to the unthinned control, PCT increased relative diameter increment of aspen saplings by 66–85% and relative basal area increment by 234–326%. Increases were similar among PCT treatments. Understory balsam fir regeneration ⩾1 m in height at time of thinning strongly benefited from PCT, with increases in height and crown width growth two to three times higher than in the control. The establishment of balsam fir regeneration, however, was not favored by PCT compared to the control. Our results show PCT increased tree size of individual aspen while promoting understory balsam fir growth in this type of stratified mixture. This approach should therefore be useful in limiting hardwood conversion in the boreal mixedwood forest at an early stage in stand development. Developing silvicultural approaches such as this one would be in line with the concept of ecosystem-based forest management.

Walnuts (Juglans spp.) are ecologically and commercially important trees, yet synthesis of past and current research findings on walnut ecophysiology is lacking, especially in terms of potential acclimation to climate change. This study aims to (1) investigate walnut ecophysiology by comparing its attributes to associated deciduous angiosperms, (2) address potential acclimation of walnut to climate change, and (3) identify areas for prioritization in future research. There is considerable uncertainty regarding the magnitude of potential effects of climate change on walnut. Some studies tend to indicate walnut could be negatively impacted by climate change, while others do not. Walnut may be at a disadvantage due to its susceptibility to drought and frost injury in current growing regions given the projected increases in temperature and extreme climatic events. Other regions that are currently considered cold for walnut growth may see increased establishment and growth depending upon the rate of temperature increase and the frequency and severity of extreme climatic events. Research investigating a combination of environmental factors, such as temperature, carbon dioxide, ozone, water, and nitrogen is needed to (1) better project climate change effects on walnut and (2) develop management strategies for walnut acclimation and adaptation to climate change.

We established a study to investigate short-term morphological responses of northern red oak (Quercus rubra L.), white oak (Quercus alba L.), and black walnut (Juglans nigra L.) to a 43% basal area reduction in a mixed planting. Although the effect was not statistically confirmed, thinned northern red oak showed a 23% gain in relative diameter growth and a 25% gain in relative crown surface area expansion compared with nonthinned trees; white oak showed gains of 15 and 10%, respectively. Similar trends were found in percentage of basal area increase for northern red oak (45%) and white oak (37%). Black walnut did not appear to respond to thinning and may have been under less competition from first-tier neighbors than the oaks were. Both northern red oak and white oak were in intermediate and suppressed crown classes, whereas black walnut was in a codominant position. Trends from this study suggest that northern red oak and white oak may respond favorably to thinning when found in lower crown classes where the amount of competition from neighboring trees is high.

Ecophysiology of black walnut ( Juglans nigra L.) along a vertical canopy gradient was studied in a mixed species plantation for the first (2007) and second (2008) growing seasons after thinning to understand response mechanisms to increased resource availability. Parameters were affected by the thinning treatment in 2008 only. Thinned trees showed increased light-saturated maximum photosynthesis ( A max ) from 2007 to 2008 compared to non-thinned trees. This response was likely due to increased light levels near thinned trees (vs. changes in water or nutrient status), because thinning did not affect midday leaf water potential ( Ψ md ), average daily soil water content (SWC), or leaf nitrogen content per unit area ( N a ). Plantation thinning did not increase relative diameter growth during the experimental period. This may be due to low thinning intensity and mortality prior to thinning that reduced competition from first-tier neighbors. Certain leaf traits such as leaf mass per unit area (LMA) and N a increased from the bottom to the upper canopy position, but did not influence thinning responses. Distribution patterns of photosynthetic parameters through the vertical canopy gradient were less defined than leaf structural traits such as LMA and N a . Findings reflect black walnut's large variability in response to thinning.

The role of lianas (woody vines) in the development and diversity of both tropical and temperate forests under differing management scenarios has not been thoroughly explored. We examined changes in grapevine (Vitis spp.) densities over time in clearcut stands as influenced by manual tending, physiography, and host tree associations. We used data from long-term studies on 66 clearcut stands dominated by temperate deciduous forest tree species on the Hoosier National Forest in south-central Indiana, USA. Fourteen of the stands had grapevines removed manually, approximately during the stem exclusion stage of development. Grapevine densities steadily increased from age 5 until age 15, which coincides with the period of stem exclusion of these stands. Subsequent grapevine mortality may have been related to light competition. Manually treated stands had similar grapevine densities as untreated stands after 20 years across sites, and it appeared that only on the most xeric area was the grapevine treatment effective in reducing grapevine densities. During early stand development, ranging from ages 5 to 17, grapevine density was strongly related to slope position, but as stands developed through the stem exclusion stage, aspect emerged as a stronger factor influencing grapevine density. Black cherry (Prunus serotina Ehrh.), walnut (Juglans spp.), and elm (Ulmus spp.) were the most common grapevine host trees under both treated and untreated scenarios, which may be associated with the crown architecture of these species. Results suggest lianas play a critical role in the early development of disturbed forest sites in temperate deciduous forests. With concerns that lianas are increasing in abundance and distribution in these forest types, understanding their role in forest dynamics, such as host tree associations at different stages of development, competition dynamics on different sites and corresponding influences on tree growth, species composition, and diversity, will be critical to decision-making processes in achieving desired management goals in the future.

Acacia gum is a complex mixture of three main components, the arabinogalactan (AG), the arabinogalactan-protein complex (AGP) and the glycoprotein (GP). In the present study, the influence of complex formation between the protein β-lactoglobulin and the Acacia gum and its two major components, the AG and AGP, on the formation of vertical macroscopic thin liquid films were investigated by means of X-ray reflectivity measurements. This method allows the determination of the thickness of the formed film and its nano-structural features. The experimental results revealed that the main effect of adding Acacia gum to a 1 g/l β-lg solution at a pH of 5.3, i.e., near the protein's pI value, is related to the formation of soluble and insoluble β-lg – arabinogalactan (AG) complexes. Addition of Acacia gum to the protein solution significantly decreased the film thickness of the formed film before it ruptured. Film experiments with fractionated Acacia gum mixtures (an AG-rich and an AG-poor, i.e., AGP-rich, fraction) or with a dialyzed Acacia gum preparation allowed to conclude that the observed influence of the Acacia gum on the thickness of the β-lg stabilized films and film stability is primarily due to the extent of complex formation between the negatively charged AG component and the β-lg. This complex formation reduces the ‘free’ β-lg concentration in the bulk which is stabilizing the two water-air surfaces in the film. The degree of complex formation considerably depends on the ionic strength in the solution. At low ionic strength, the negative charges on the AG are not screened by the salt ions leading to extensive electrostatic complex formation (formation of soluble and/or insoluble complexes) with the β-lg, even at the isoelectric point of the protein. However, if the ionic strength in the β-lg – Acacia gum mixture is in the sub-millimolar range, significant charge screening effects are occurring keeping the arabinogalactan component away from complexation with the β-lg molecules and allowing the formation of stable thin liquid films up to a β-lg – Acacia gum weight ratio of 2:1. Addition of more Acacia gum under these ionic strength conditions resulted again in the formation of unstable thin films.

Fermentation of a reconstituted skim milk concentrate (8% protein) was investigated to elucidate the effects of various fermentation parameters on the structural, rheological and visual (wheying-off) properties of the resulting gels (pH 4.60). Fermentation trials were performed with non-exocellular polysaccharide-producing strains of Streptococcus thermophilus at various fermentation temperatures and at various chymosin levels. Oscillatory vane rheometry carried out on the intact gels (at 4 °C) showed that the level of chymosin had a significant impact on the gel strength (storage modulus G ′). This can be explained by the arrangement of casein micelles into more compact aggregates and the enhanced fusion of aggregated casein micelles as revealed by transmission electron microscopy for the gels fermented with chymosin. Wheying-off of the stirred gels as measured by a centrifugation test (at 4 °C) and pore size of the intact gel structures investigated by scanning electron microscopy both increased with increasing level of chymosin and increasing fermentation temperature (resulting in an increase in acidification rate). A higher level of syneresis (wheying-off) is explained by the larger pore size, since larger pores present a lower resistance to the outflow of whey from the gel.

We evaluated the effectiveness of commercial thinning mainly from below (CT, 0, 26%, 32% and 40% merchantable basal area removals) in meeting wood production demands and developing structural heterogeneity in a balsam fir (Abies balsamea (L.) Mill) and spruce (Picea spp.) stand. After 10 years, 32%–40% removals showed a 12%–18% increase in mean diameter and 27%–38% increase in gross merchantable volume (GMV) per tree compared to the unthinned control. At the stand level, all thinning treatments generated as much cumulative GMV (harvested volume + GMV after 10 years) and gross sawlog volume per hectare as the unthinned control. As for stand structure, eight out of nine thinned experimental units showed increased structural heterogeneity after 10 years, i.e., irregular, positively-skewed diameter distribution with an elongated right tail toward larger trees. The diameter distribution in the unthinned control became more symmetric, unimodal and regular over time, with fewer saplings than at the beginning of the experiment and lower density of larger trees compared to CT. Regeneration density and stocking were abundant in all treatments, largely dominated by balsam fir. Results indicate that thinning can be used to meet wood production objectives and help develop structural heterogeneity in this forest.

A food material science approach using microscopy, rheology and denaturation assessment of proteins was applied to describe the behaviour of mixtures of a whey protein isolate (WPI) and a high methoxy pectin (HM-pectin) upon high-pressure treatment (200 to 800 MPa at 25 or 40 °C and holding time of 10 min). The results of high-pressure treatment were compared to a pure heat treatment at 75 °C (5–20 min) and 85 °C (10 min). Similar textures could be obtained after high-pressure treatment of the mix at ambient temperature at all pressure levels tested (200–800 MPa) and after temperature treatments at 75 °C up to 10 min. Significant changes were only obtained in phase separating WPI/HM-pectin mixtures if treated at 40 °C and pressures>400 MPa and after heat-treatment at 85 °C for 10 min, where total WPI denaturation was above 60%. Under such conditions the protein-enriched phase gelled and significantly changed the overall texture as measured by rheology. In the presence of pectin, protein denaturation was decreased in both pressure and temperature treated samples. Microscopic analysis showed that structure formation depends on the processing history. Compared to a pure heat treatment, pressure offers a greater flexibility for fine-tuning the protein denaturation due to an increased freedom in processing parameters (pressure, holding time and temperature).

Azimuthal correlations of photons produced at mid-rapidity in 200 A GeV S + Au collisions have been studied using a preshower photon multiplicity detector in the WA93 experiment. The Fourier expansion method has been employed to estimate the event plane via the anisotropy of the event as a function of centrality. The event plane correlation technique has been used to determine the true event anisotropy, beyond the anisotropy which arises due to finite multiplicity. The VENUS event generator with rescattering and proper simulation of the detector response can explain only a portion of the observed anisotropy. The residual anisotropy is found to be of the order of 5% for semi-central collisions. This suggests that directed collective flow of the produced particles is present at SPS energies. (C) 1997 Published by Elsevier Science B.V.

The mean transverse momentum of photons has been determined on an event by event basis in S + Au collisions at 200 A.GeV from the ratio of the measured electromagnetic transverse energy (E-T(em)) to the photon multiplicity (N-gamma). The average value obtained is similar to that determined for the same system using spectroscopic techniques. The centrality dependence of the measured values are in agreement with the predictions of the VENUS event generator. (C) 1997 Published by Elsevier Science B.V.