Publications by authors named "David A King"

65 Publications

Particle shapes leading to Newtonian dilute suspensions.

Phys Rev E 2020 Sep;102(3-1):032615

Cavendish Laboratory, University of Cambridge, J. J. Thomson Ave., Cambridge CB3 0HE, United Kingdom.

It is well known that suspensions of particles in a viscous fluid can affect the rheology significantly, producing a pronounced non-Newtonian response even in dilute suspension. However, it is unclear a priori which particle shapes lead to this behavior. We present two simple symmetry conditions on the shape which are sufficient for a dilute suspension to be Newtonian for all strain sizes and one sufficient for Newtonian behavior for small strains. We also construct a class of shapes out of thin, rigid rods not found by the symmetry argument which share this property for small strains.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevE.102.032615DOI Listing
September 2020

Effects of space allowance and marketing strategy on growth performance of pigs raised to 165 kg.

Transl Anim Sci 2020 Apr 18;4(2):txaa065. Epub 2020 May 18.

Pig Improvement Company, Hendersonville, TN.

A total of 976 pigs (PIC 327 × Camborough; PIC, Hendersonville, TN; initially 22.0 ± 1.53 kg body weight [BW]) were used in a 160-d growth study to evaluate the effects of increasing space allowance and varying marketing strategies on growth performance of pigs raised to market weights of ~165 kg. Pens of pigs were blocked by location within the barn and allotted to one of six treatments. Pen served as the experimental unit, and there were eight replicate pens per treatment. The first four treatments consisted of increased initial stocking density and did not utilize topping strategies: (1) 14 pigs/pen (1.17 m/pig), (2) 17 pigs/pen (0.97 m/pig), (3) 20 pigs/pen (0.82 m/pig), and (4) 23 pigs/pen (0.71 m/pig). The fifth treatment began with 25 pigs/pen (0.66 m/pig) and had four marketing events with the heaviest 3 pigs/pen removed on day 93, and additional pigs removed to a common inventory of 20 pigs/pen on day 122 and 17 pigs/pen on day 147 with final marketing on day 160. The final treatment began the experiment with 23 pigs/pen (0.71 m/pig) with three marketing events to achieve a common inventory of 20 pigs/pen on day 108 and 17 pigs/pen on day 147. Pens of pigs were weighed and feed disappearance measured on days 0, 55, 93, 108, 122, 135, 147, and 160. As space allowance decreased from 1.17 to 0.71 m/pig via increased initial pen inventory (treatments 1 to 4), overall average daily gain (ADG) and average daily feed intake (ADFI) decreased (linear, < 0.001), while gain:feed ratio (G:F) did not differ ( > 0.05). The treatments with multiple marketing events were compared with each other and with the treatment that began with 0.71 m/pig and only marketed once at the end of the study. Overall ADG and ADFI were not different ( > 0.05) among these three treatments. Marketing pigs three or four times improved ( < 0.05) G:F compared with the treatment that began the study with 0.71 m/pig and marketed only once. Reducing floor space allowance for heavy weight pigs decreased intake, which resulted in lower growth rate and final BW, with these reductions occurring before the critical -value was reached. Total weight gain per pen was maximized with the lowest space allowance and the multiple marketing treatments. Thus, strategic use of pig removals prior to final marketing may allow producers to maximize both number of pigs and total weight marketed through a barn when feeding to heavy weights.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/tas/txaa065DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7277694PMC
April 2020

Evaluation of UVC Radiation and a UVC-Ozone Combination as Fresh Beef Interventions against Shiga Toxin-Producing Escherichia coli, Salmonella, and Listeria monocytogenes and Their Effects on Beef Quality.

J Food Prot 2020 Sep;83(9):1520-1529

U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska 68933-0166, USA.

Abstract: This research study was conducted to evaluate treatments with UVC light and a combination of UVC and ozone that have recently received attention from the beef processing industry as antimicrobial interventions that leave no chemical residues on products. The effectiveness of UVC and UVC plus gaseous ozone treatments was evaluated for inactivation of pathogenic bacteria on fresh beef and for any impact on fresh beef quality. Fresh beef tissues were inoculated with cocktails of Shiga toxin-producing Escherichia coli (STEC) strains (serotypes O26, O45, O103, O111, O121, O145, and O157:H7), Salmonella, and Listeria monocytogenes. Inoculated fresh beef tissues were subjected to UVC or UVC-ozone treatments at 106 to 590 mJ/cm2. UVC treatment alone or in combination with ozone reduced populations of STEC, Salmonella, L. monocytogenes, and aerobic bacteria from 0.86 to 1.49, 0.76 to 1.33, 0.5 to 1.14, and 0.64 to 1.23 log CFU, respectively. Gaseous ozone alone reduced populations of E. coli O157:H7, Salmonella, and L. monocytogenes by 0.65, 0.70, and 0.33 log CFU, respectively. Decimal reduction times (D-values) for STEC serotypes, Salmonella, and L. monocytogenes on surfaces of fresh beef indicated that the UVC-ozone treatment was more effective (P ≤ 0.05) than UVC light alone for reducing pathogens on the surface of fresh beef. Exposure to UVC or UVC plus gaseous ozone did not have a deleterious effect on fresh meat color and did not accelerate the formation of oxidative rancidity. These findings suggest that UVC and UVC in combination with gaseous ozone can be useful for enhancing the microbial safety of fresh beef without impairing fresh beef quality.

Highlights:
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4315/JFP-19-473DOI Listing
September 2020

Prevalence of Extreme Heat-Resistant Gram-Negative Bacteria Carried by U.S. Cattle at Harvest.

J Food Prot 2020 Aug;83(8):1438-1443

U.S. Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, P.O. Box 166, State Spur D, Clay Center, Nebraska 68933, USA.

Abstract: Prevalence of heat-resistant bacteria in beef poses a potential problem as thermal interventions are routinely used in beef processing to control contamination. Despite extreme heat-resistant (XHR) Escherichia coli having been isolated from a ground beef processing plant, there has not been a study to assess the prevalence of XHR E. coli among types of cattle. Therefore, this study used a screening assay for XHR gram-negative bacteria and its molecular determinant, the locus of heat resistance (LHR), on feces collected from U.S. cattle. Fecal samples were collected from fed (n = 538), cull dairy (n = 425), and cull beef (n = 475) cattle at nine regional beef processing plants located across the United States. Among the 1,438 cattle sampled from northern (n = 288), southern (n = 288), eastern (n = 287), western (n = 287), and central (n = 288) regions of the United States, 91 (6.3%) cattle showed presence of XHR bacteria, as evident by growth in MacConkey broth following heat treatment of 80°C for 15 min, in their feces. Heat-resistant bacteria (n = 140) were isolated from the 91 fecal samples. Prevalence of XHR bacteria was highest (11%) in cattle from the northern region. Ninety percent of the XHR isolates were identified as E. coli. Multiplex PCR of all 1,438 fecal samples showed that the LHR was absent in 40.7% of samples and intact in 18.7% of samples. Despite the higher prevalence of intact LHR from PCR analysis, only 11 samples (0.8%) were confirmed to contain bacteria with an intact LHR. The LHR was absent in 91% of XHR bacteria, and only 7.9% of XHR bacteria had intact LHR, suggesting a novel mechanism of heat resistance. By developing and using the screening assays, we established the prevalence of XHR bacteria (6.3%) and LHR+ bacteria (0.8%) in U.S. beef cattle.

Highlights:
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4315/JFP-20-103DOI Listing
August 2020

Effect of hot carcass weight on the rate of temperature decline of pork hams and loins in a blast-chilled commercial abattoir123.

J Anim Sci 2019 May;97(6):2441-2449

Department of Animal Sciences, University of Illinois, Urbana-Champaign, IL 61801.

Adequate carcass chilling is required to optimize pork quality and food safety. The rate at which carcasses chill is dependent on their mass. Hot carcass weight has increased steadily over the years, certainly affecting the chilling rate of the average carcass in contemporary abattoirs. Therefore, the objective was to model the effect of HCW on temperature decline of a contemporary population of pork carcasses slaughtered at a commercial abattoir that used a blast-chilling method. In addition, carcasses were sorted into HCW classes, and the effect of HCW group was tested on the rate of temperature decline of the longissimus dorsi and semimembranosus. Hot carcass weight, internal temperature of the loin muscle (at the 10th rib) and ham, as well as ambient temperature, were recorded from 40 to 1,320 min postmortem (45 time points) on 754 pork carcasses. An exponential decay model based on Newton's law of cooling,  T(t)=Ta+(T0-Ta)e-kt, was fit to temperature decline of the ham and loin of the whole population using PROC MODEL of SAS. The initial models for the decline of both ham and loin temperature displayed significant autocorrelation of errors based on evaluation of the autocorrelation function plots and Durbin-Watson test (P < 0.0001). Therefore, second- and third-order autocorrelation parameters were tested. Based on Durbin-Watson test, the use of second-order autocorrelation model with lags of 1 and 2 was deemed adequate and was therefore included in all subsequent models. This base model and its respective parameter estimates were all significant (P < 0.01) for the whole population. Carcasses approximating 85, 90, 95, 100, and 105 kg (± 1 kg) were selected and binned into their respective weight classes. Dummy variables were used to compare the effect of HCW class on parameter estimate of ham and loin models. The developed model significantly fit all weight classes (P < 0.01) for both ham and loin temperature decline. For both loin and ham models, estimates of the rate constant (k) generally decreased as HCW increased. For loin temperature, k estimate for 105-kg carcasses was 0.00124 less (P = 0.02) than 85-kg carcasses, with the intermediate HCW classes not differing from the 85-kg class. For ham temperature, estimates of k for 90, 95, 100, and 105 kg HCW were all significantly and successively less than the k estimate for 85 kg class. For perspective, loins of 95-kg carcasses were estimated to reach 2 °C in 17 h, whereas loins from 105-kg carcasses would not reach 2 °C until 27 h. For hams, 95-kg carcasses were projected to reach 2 °C in 21 h, whereas those from 105-kg carcasses would take 28 h. Overall, HCW significantly affects the rate of temperature decline of pork hams, but not loins from pork carcasses weighing between 85 and 100 kg.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/jas/skz131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6541802PMC
May 2019

Enhanced estimates of carcass and meat quality effects for polymorphisms in myostatin and µ-calpain genes.

J Anim Sci 2019 Feb;97(2):569-577

USDA, Agricultural Research Service, Roman L. Hruska US Meat Animal Research Center, Clay Center, NE.

The objective of this study was to enhance estimates of additive, dominance, and epistatic effects of marker polymorphisms on beef carcass and quality traits. Myostatin (MSTN) F94L SNP and the µ-calpain (CAPN1) 316 and 4751 SNP haplotype have previously been associated with fat and muscle traits in beef cattle. Multiyear selection in a composite population segregating these polymorphisms increased minor allele (F94L L) and chosen haplotype (CAPN1 CC and GT) frequencies to intermediate levels resulting in more precise estimates of additive and nonadditive genetic effects. During the 3 yr after selection, 176 steers were evaluated for growth, carcass, meat quality, tenderness (n = 103), and meat color traits. The statistical model included year, age of dam, age of the steer, and genotype in a random animal model. The 9 genotypes (3 CAPN1 diplotypes × 3 F94L genotypes) affected marbling score, ribeye area, adjusted fat thickness, vision yield grade (all P < 0.001), slice shear force (P = 0.03), and CIE L* reflectance (P = 0.01). Linear contrasts of the 9 genotypes estimated additive, recessive, and epistatic genetic effects. Significant additive effects of the F94L L allele decreased marbling score, adjusted fat thickness, vision yield grade, and slice shear force; and increased ribeye area and CIE L* reflectance. The homozygous F94L FF and LL genotypes differed by 1.3 to 1.9 phenotypic SD for most carcass traits and by 0.8 to 0.9 SD for slice shear force and CIE L* reflectance but carcass weight differed by only 3 kg (0.1 SD). The L allele was partially recessive to F for ribeye area (P = 0.02) and the heterozygous FL means tended to be closer to the FF genotype than the LL genotype for other carcass traits but differences from additive were not significant. The CAPN1 additive × F94L additive effect on slice shear force was the only significant epistatic estimate. The F94L L allele is prevalent in Limousin but nearly absent in other U.S. purebreds. This allele had about half of the effects on birth weight, muscle, and fat traits reported for severe MSTN mutations in Belgian Blue and Piedmontese breeds. The interaction between MSTN and CAPN1 genotypes may reflect the strong additive effects of MSTN F94L L allele on fat and muscle traits interfering with the phenotypic effect of CAPN1 genotype on meat tenderness.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/jas/sky451DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6358262PMC
February 2019

Effects and interactions of myostatin and callipyge mutations: I. Growth and carcass traits.

J Anim Sci 2018 Mar;96(2):454-461

USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE.

Objectives were to document effects of the Texel myostatin mutation (MSTN) on growth and carcass traits and also test whether or not interactions with the callipyge mutation (CLPG) could be detected. Twelve rams heterozygous at both loci on the two different chromosomes were mated to 215 terminal-sire type composite crossbred ewes genotyped as non-carriers for both loci. A total of 365 lambs were born, 362 of those were genotyped and 236 lambs contributed carcass data to estimate effects and interactions among the four genotype combinations produced. The four genotype combinations were defined as follows: ++/++ for wild-type at both loci; ++/C+ for wild-type at MSTN and heterozygous at CLPG; M+/++ for heterozygous at MSTN and wild-type at CLPG; and M+/C+ for heterozygous at both loci. The two independently segregating sire-derived alleles represent different breed-of-origin contrasts at each locus (Texel vs. composite origin for MSTN and Dorset vs. Texel origin for CLPG). Birth weight was recorded on all lambs, and subsequent body weights were adjusted to 56 (weaning), 70, and 140 d of age. Within sire-sex-genotype subgroups, naturally reared lambs were assigned to one of eight slaughter groups accounting for variation in birth date. Lambs were serially slaughtered at weekly intervals, 30 lambs per group, from roughly 26 to 33 wk of age. In addition to standard carcass traits, subjective leg scores were assigned and widths of carcasses were measured at the widest points of the shoulder and rump. Differences in birth weight were detected (P < 0.01) for the combination of the two loci and birth type, with single-born differences among genotypes exceeding differences among twin born progeny. Those interaction differences among genotypes were not as important at weaning (P = 0.36). Impact on growth rate differences among the genotypes during the post-weaning period were variable and dependent on sex of the lamb (P < 0.01). A synergistic interaction between MSTN and CLPG was observed for leg muscling scores (P < 0.05) but no other measures of carcass shape were affected. One copy of MSTN had a more modest impact on fat deposition and muscle conformation than did CLPG and did not interact (all values P > 0.20). Although some non-additive interactions that vary by trait and sex were detected, in general the data are consistent with the two mutations acting on muscle growth through independent pathways.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/jas/skx055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6140951PMC
March 2018

Biofilm Formation, Antimicrobial Resistance, and Sanitizer Tolerance of Salmonella enterica Strains Isolated from Beef Trim.

Foodborne Pathog Dis 2017 12 16;14(12):687-695. Epub 2017 Oct 16.

Roman L. Hruska U.S. Meat Animal Research Center, Agricultural Research Service, U.S. Department of Agriculture, Clay Center , Nebraska.

In the beef industry, product contamination by Salmonella enterica is a serious public health concern, which may result in human infection and cause significant financial loss due to product recalls. Currently, the precise mechanism and pathogen source responsible for Salmonella contamination in commercial establishments are not well understood. We characterized 89 S. enterica strains isolated from beef trim with respect to their biofilm-forming ability, antimicrobial resistance, and biofilm cell survival/recovery growth after sanitizer exposure. A total of 28 Salmonella serovars was identified within these strains. The most common serovars identified were Anatum, Dublin, Montevideo, and Typhimurium, with these accounting for nearly half of the total strains. The vast majority (86%) of the strains was able to develop strong biofilms, and the biofilm-forming ability was highly strain dependent and related to cell surface expression of extracellular polymeric structures. These strains also demonstrated strong tolerance to quaternary ammonium chloride (QAC) and chlorine dioxide (ClO), but were more sensitive to chlorine treatment. Sanitizer tolerance and bacterial postsanitization recovery growth were closely associated with strains' biofilm-forming ability. Thirty percent of the examined strains were found resistant to multiple antimicrobial agents and the resistance phenotypes were serovar associated, but not related to strains' biofilm-forming ability. Pulsed-field gel electrophoresis analysis tended to group strains by serovar rather than by biofilm-forming ability. Collectively, these data indicate that the strong biofilm formers of certain S. enterica strains/serovars possess significant potential for causing meat product contamination in meat processing environment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/fpd.2017.2319DOI Listing
December 2017

STAAR: a randomised controlled trial of electronic adherence monitoring with reminder alarms and feedback to improve clinical outcomes for children with asthma.

Thorax 2017 04 4;72(4):347-354. Epub 2016 Nov 4.

School of Paediatrics and Child Health, Princess Margaret Hospital University of Western Australia, Perth, Western Australia, Australia.

Background: Suboptimal adherence to inhaled steroids is common in children with asthma and is associated with poor disease control, reduced quality of life and even death. Previous studies using feedback of electronically monitored adherence data have demonstrated improved adherence, but have not demonstrated a significant impact on clinical outcomes. The aim of this study was to determine whether introduction of this approach into routine practice would result in improved clinical outcomes.

Methods: Children with asthma aged 6-16 years were randomised to the active intervention consisting of electronic adherence monitoring with daily reminder alarms together with feedback in the clinic regarding their inhaled corticosteroid (ICS) use or to the usual care arm with adherence monitoring alone. All children had poorly controlled asthma at baseline, taking ICS and long-acting β-agonists. Subjects were seen in routine clinics every 3 months for 1 year. The primary outcome was the Asthma Control Questionnaire (ACQ) score. Secondary outcomes included adherence and markers of asthma morbidity.

Results: 77 of 90 children completed the study (39 interventions, 38 controls). Adherence in the intervention group was 70% vs 49% in the control group (p≤0.001). There was no significant difference in the change in ACQ, but children in the intervention group required significantly fewer courses of oral steroids (p=0.008) and fewer hospital admissions (p≤0.001).

Conclusions: The results indicate that electronic adherence monitoring with feedback is likely to be of significant benefit in the routine management of poorly controlled asthmatic subjects.

Trial Registration Number: NCT02451709; pre-result.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/thoraxjnl-2015-208171DOI Listing
April 2017

Lessons Learned on the Presentation of Scan Data.

Health Phys 2015 Nov;109(3 Suppl 3):S212-8

* Oak Ridge Associated Universities, 1299 Bethel Valley Road, Oak Ridge, TN.

Technicians performed a radiological survey of a surplus metal tank to support disposition planning at an Oak Ridge, TN, site. The survey included radiation scans to identify contamination and, if identified, define the boundary and magnitude of contamination. Fixed-point 1-min measurements were also collected at randomly selected locations for comparison against the site's free release limit of 5,000 disintegrations per minute per 100 cm (dpm 100 cm) (0.83 Bq cm). Scan data were recorded using a data logger as a means to document surveyor observation-logged data captured at 1-s intervals and converted to counts per minute (cpm) by the data logger software were presented in the project report. Both the qualitative scan data (in cpm) and the quantitative direct measurements (in dpm 100 cm) were reported for completeness, so stakeholders had all available information to support disposition decisions. However, a new stakeholder-introduced to the project at the reporting phase of work-used the instrument efficiency and background data to convert the scan data from cpm to dpm 100 cm, then compared the converted results to the site limit. Many of the converted values exceeded 5,000 dpm 100 cm. This resulted in delays in tank disposition and additional project costs that could have been avoided if the proper use and interpretation of scan data and implications of radon progeny buildup on oxidized metal surfaces had been better communicated.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/HP.0000000000000358DOI Listing
November 2015

Biofilm formation and sanitizer resistance of Escherichia coli O157:H7 strains isolated from "high event period" meat contamination.

J Food Prot 2014 Nov;77(11):1982-7

U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska 68933-0166, USA.

In the meat industry, a "high event period" (HEP) is defined as a time period during which commercial meat plants experience a higher than usual rate of Escherichia coli O157:H7 contamination. Genetic analysis indicated that within a HEP, most of the E. coli O157:H7 strains belong to a singular dominant strain type. This was in disagreement with the current beef contamination model stating that contamination occurs when incoming pathogen load on animal hides, which consists of diverse strain types of E. coli O157:H7, exceeds the intervention capacity. Thus, we hypothesize that the HEP contamination may be due to certain in-plant colonized E. coli O157:H7 strains that are better able to survive sanitization through biofilm formation. To test our hypothesis, a collection of 45 E. coli O157:H7 strains isolated from HEP beef contamination incidents and a panel of 47 E. coli O157:H7 strains of diverse genetic backgrounds were compared for biofilm formation and sanitizer resistance. Biofilm formation was tested on 96-well polystyrene plates for 1 to 6 days. Biofilm cell survival and recovery growth after sanitization were compared between the two strain collections using common sanitizers, including quaternary ammonium chloride, chlorine, and sodium chlorite. No difference in "early stage" biofilms was observed between the two strain collections after incubation at 22 to 25°C for 1 or 2 days. However, the HEP strains demonstrated significantly higher potency of "mature" biofilm formation after incubation for 4 to 6 days. Biofilms of the HEP strains also exhibited significantly stronger resistance to sanitization. These data suggest that biofilm formation and sanitization resistance could have a role in HEP beef contamination by E. coli O157:H7, which highlights the importance of proper and complete sanitization of food contact surfaces and food processing equipment in commercial meat plants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4315/0362-028X.JFP-14-253DOI Listing
November 2014

Response to Comment on "Effects of ethanol on vehicle energy efficiency and implications on ethanol life-cycle greenhouse gas analysis".

Environ Sci Technol 2014 Aug 4;48(16):9953-4. Epub 2014 Aug 4.

Environment and Sustainability Institute, University of Exeter , Penryn, Cornwall TR10 9FE, United Kingdom.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/es503420yDOI Listing
August 2014

Climate change and fire effects on a prairie-woodland ecotone: projecting species range shifts with a dynamic global vegetation model.

Ecol Evol 2013 Dec 18;3(15):5076-97. Epub 2013 Nov 18.

US Geological Survey Hot Springs, South Dakota, USA.

Large shifts in species ranges have been predicted under future climate scenarios based primarily on niche-based species distribution models. However, the mechanisms that would cause such shifts are uncertain. Natural and anthropogenic fires have shaped the distributions of many plant species, but their effects have seldom been included in future projections of species ranges. Here, we examine how the combination of climate and fire influence historical and future distributions of the ponderosa pine-prairie ecotone at the edge of the Black Hills in South Dakota, USA, as simulated by MC1, a dynamic global vegetation model that includes the effects of fire, climate, and atmospheric CO2 concentration on vegetation dynamics. For this purpose, we parameterized MC1 for ponderosa pine in the Black Hills, designating the revised model as MC1-WCNP. Results show that fire frequency, as affected by humidity and temperature, is central to the simulation of historical prairies in the warmer lowlands versus woodlands in the cooler, moister highlands. Based on three downscaled general circulation model climate projections for the 21st century, we simulate greater frequencies of natural fire throughout the area due to substantial warming and, for two of the climate projections, lower relative humidity. However, established ponderosa pine forests are relatively fire resistant, and areas that were initially wooded remained so over the 21st century for most of our future climate x fire management scenarios. This result contrasts with projections for ponderosa pine based on climatic niches, which suggest that its suitable habitat in the Black Hills will be greatly diminished by the middle of the 21st century. We hypothesize that the differences between the future predictions from these two approaches are due in part to the inclusion of fire effects in MC1, and we highlight the importance of accounting for fire as managed by humans in assessing both historical species distributions and future climate change effects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ece3.877DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3892370PMC
December 2013

Medical image. Hereditary haemorrhagic telangiectasia.

N Z Med J 2013 Dec 13;126(1387):179-81. Epub 2013 Dec 13.

Sheffield Children's Hospital, Sheffield, United Kingdom.

View Article and Find Full Text PDF

Download full-text PDF

Source
December 2013

Non-dissociative activation of chemisorbed dinitrogen on Ni{110} by co-adsorbed lithium.

J Chem Phys 2013 Nov;139(18):184708

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.

Weakening the intramolecular N-N bond is essential to promote direct hydrogenation of adsorbed N2 on catalyst surfaces. The interaction of N2 with Li on Ni{110} surfaces has been investigated. We show that the N-N bond is significantly weakened with increasing Li coverage, evidenced by large redshifts in N-N stretch frequency of up to 380 cm(-1) compared to the gas phase. Some increased thermal stability of the most weakened N2,ads states is also observed. We speculate that the various observed redshifts in N-N stretch frequency are associated with an enhanced backfilling of the 2π* antibonding orbital of N2 due to both the Li-induced surface electrostatic field, and the formation of Lix(N2)y surface complexes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.4829067DOI Listing
November 2013

Impact of sampling area and location on measurement of indicator organisms during beef carcass interventions.

J Food Prot 2013 Dec;76(12):2069-73

U.S. Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, P.O. Box 166, State Spur 18D, Clay Center, Nebraska 68933, USA.

The effect of the sponge sample collection site on the recovery of multiple indicator organisms from beef carcass surfaces was evaluated to simplify and validate our previous sampling method for ease of implementation as a general protocol. Sponge samples were collected at three beef processing plants using hot water or acidic antimicrobials as interventions. Two 4,000-cm(2) samples were collected from preevisceration carcasses (n = 248), one from the inside and outside round area (top site) and one from the navel-plate-brisket-foreshank area (bottom site). One-half of the samples (n = 124) were collected before a wash cabinet intervention and the other half after the intervention. The numbers of total aerobic bacteria, Enterobacteriaceae, coliforms, and Escherichia coli were determined for one-half of each individual sponge sample. The other halves of the sponges were combined to represent a top plus bottom 8,000-cm(2) SAMPLE: For the preintervention carcasses, 4,000-cm(2) samples collected from the top or bottom sites of the carcasses were not significantly different (P > 0.05) from each other or from the 8,000-cm(2) combined sample in recovery of the indicator organisms. Significant reductions of indicator organisms were observed in all three types of sponge samples after intervention; however, samples collected from the bottom site recovered less organisms (P < 0.05) compared with samples of the other types. These results suggested that samples collected from either the top or the bottom site of the carcasses with this method are suitable for monitoring indicator organisms as long as the same sampling site is consistently used.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4315/0362-028X.JFP-13-134DOI Listing
December 2013

Effects of ethanol on vehicle energy efficiency and implications on ethanol life-cycle greenhouse gas analysis.

Environ Sci Technol 2013 Jun 14;47(11):5535-44. Epub 2013 May 14.

Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK.

Bioethanol is the world's largest-produced alternative to petroleum-derived transportation fuels due to its compatibility within existing spark-ignition engines and its relatively mature production technology. Despite its success, questions remain over the greenhouse gas (GHG) implications of fuel ethanol use with many studies showing significant impacts of differences in land use, feedstock, and refinery operation. While most efforts to quantify life-cycle GHG impacts have focused on the production stage, a few recent studies have acknowledged the effect of ethanol on engine performance and incorporated these effects into the fuel life cycle. These studies have broadly asserted that vehicle efficiency increases with ethanol use to justify reducing the GHG impact of ethanol. These results seem to conflict with the general notion that ethanol decreases the fuel efficiency (or increases the fuel consumption) of vehicles due to the lower volumetric energy content of ethanol when compared to gasoline. Here we argue that due to the increased emphasis on alternative fuels with drastically differing energy densities, vehicle efficiency should be evaluated based on energy rather than volume. When done so, we show that efficiency of existing vehicles can be affected by ethanol content, but these impacts can serve to have both positive and negative effects and are highly uncertain (ranging from -15% to +24%). As a result, uncertainties in the net GHG effect of ethanol, particularly when used in a low-level blend with gasoline, are considerably larger than previously estimated (standard deviations increase by >10% and >200% when used in high and low blends, respectively). Technical options exist to improve vehicle efficiency through smarter use of ethanol though changes to the vehicle fleets and fuel infrastructure would be required. Future biofuel policies should promote synergies between the vehicle and fuel industries in order to maximize the society-wise benefits or minimize the risks of adverse impacts of ethanol.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/es305209aDOI Listing
June 2013

An approach for addressing hard-to-detect hot spots.

Health Phys 2013 May;104(5 Suppl 2):S52-9

Oak Ridge Associated Universities, P.O. Box 117, MS-22, Oak Ridge, TN 37831, USA.

The Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) survey approach is comprised of systematic random sampling coupled with radiation scanning to assess acceptability of potential hot spots. Hot spot identification for some radionuclides may not be possible due to the very weak gamma or x-ray radiation they emit-these hard-to-detect nuclides are unlikely to be identified by field scans. Similarly, scanning technology is not yet available for chemical contamination. For both hard-to-detect nuclides and chemical contamination, hot spots are only identified via volumetric sampling. The remedial investigation and cleanup of sites under the Comprehensive Environmental Response, Compensation, and Liability Act typically includes the collection of samples over relatively large exposure units, and concentration limits are applied assuming the contamination is more or less uniformly distributed. However, data collected from contaminated sites demonstrate contamination is often highly localized. These highly localized areas, or hot spots, will only be identified if sample densities are high or if the environmental characterization program happens to sample directly from the hot spot footprint. This paper describes a Bayesian approach for addressing hard-to-detect nuclides and chemical hot spots. The approach begins using available data (e.g., as collected using the standard approach) to predict the probability that an unacceptable hot spot is present somewhere in the exposure unit. This Bayesian approach may even be coupled with the graded sampling approach to optimize hot spot characterization. Once the investigator concludes that the presence of hot spots is likely, then the surveyor should use the data quality objectives process to generate an appropriate sample campaign that optimizes the identification of risk-relevant hot spots.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/HP.0b013e3182812867DOI Listing
May 2013

Single-crystal adsorption calorimetry and density functional theory of CO chemisorption on fcc Co{110}.

Phys Chem Chem Phys 2013 Mar;15(11):4059-65

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

Using single-crystal adsorption calorimetry (SCAC) and density functional theory (DFT), the interaction of carbon monoxide on fcc Co{110} is reported for the first time. The results indicate that adsorption is consistent with molecular chemisorption at all coverages. The initial heat of adsorption of 140 kJ mol(-1) is found in the range of heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron. DFT adsorption energies are in good agreement with the experimental results, and comparison between SCAC and DFT for CO on other ferromagnetic surfaces is made. The calculated dissociation barrier of 2.03 eV implies that dissociation at 300 K is unlikely even at the lowest coverage. At high coverages during the adsorption-desorption steady state regime, a pre-exponential factor for CO desorption of 1.2 × 10(17) s(-1) is found, implying a localised molecular adsorbed state prior to desorption in contrast to what we found with Ni surfaces. This result highlights the importance of the choice of the pre-exponential factor in evaluating the activation energy for desorption.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c3cp43836hDOI Listing
March 2013

Structural phases formed by NO2/CO co-adsorption on Au{111} surfaces.

J Chem Phys 2012 Aug;137(7):074703

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.

Exposing a Au{111} surface to NO(2) and then to CO at temperatures around 120 K in ultra-high vacuum gives rise to molecular overlayers in which the two species are co-adsorbed, which we have investigated using low-temperature scanning tunnelling microscopy. Under NO(2)-rich conditions, a (√7 × √7)R19.1° phase with 3:1 NO(2):CO stoichiometry forms. Under CO-rich conditions, this phase co-exists with other phases having 2:1 and 1:1 NO(2):CO stoichiometries and different symmetries, and with bare Au surface. Structural models for these phases are discussed. Individual domains of the (√7 × √7)R19.1° phase are chiral, by virtue of the arrangement of their achiral components, an observation that may have more general implications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.4743901DOI Listing
August 2012

Nitrogen adsorption and desorption at iron pyrite FeS2{100} surfaces.

Phys Chem Chem Phys 2012 Aug 17;14(32):11491-9. Epub 2012 Jul 17.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.

We have investigated the interaction of nitrogen with single-crystal iron pyrite FeS(2){100} surfaces in ultra-high vacuum. N(2) adsorbs molecularly at low temperatures, desorbing at 130 K, but does not adsorb dissociatively even at pressures up to 1 bar. Atomic surface N can, however, be obtained with nitrogen ions and/or excited neutral species, generated by passing N(2) through an ion gun. Substantial nitrogen-induced disorder is seen with both ions and neutrals, and no ordered N overlayers form; a decrease in the S/Fe ratio is seen when exposing to nitrogen ions. Recombinative desorption leads to temperature-programmed desorption peaks at 410 and 520-560 K which we associate with interstitial atomic N and substitutional ionic N, respectively, in the surface regions. Thermal repair of sputter damage necessitates segregation of bulk S to the surface, which, over repeated experiments, leads to gross cumulative damage to the bulk crystal. The desorption temperatures associated with recombinative desorption of atomic N from FeS(2){100} are significantly lower than those measured for Fe surfaces. This is linked to the inability of FeS(2){100} to dissociate N(2), but suggests that N(ads) will be significantly more able to react with other species than it is on Fe surfaces.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c2cp41549fDOI Listing
August 2012

Microcalorimetry of oxygen adsorption on fcc Co{110}.

Phys Chem Chem Phys 2012 May 24;14(20):7528-32. Epub 2012 Apr 24.

Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.

The coverage dependent heats of adsorption and sticking probabilities for oxygen on fcc Co{110} have been measured at 300 K using single crystal adsorption calorimetry (SCAC). Initial adsorption is consistent with dissociative chemisorption at low coverage followed by oxide formation above 0.6 ML coverage. The initial heat of adsorption of 633 kJ mol(-1) is similar to heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron. As the coverage increases, the heat of adsorption and sticking probability drop very rapidly up to the onset of oxidation. As already observed for other oxygen-metal surface systems, strong lateral adatom repulsions are responsible for the transition from the chemisorption regime to oxide film formation at higher coverage. The heat of oxide formation at the onset is 475 kJ mol(-1), which is consistent with the formation of CoO crystallites. The oxide film formation is discussed in terms of nucleation and island growth, and the Mott-Cabrera mechanisms, the latter being evidenced by the relatively constant heat of adsorption and sticking probability in contrast to the nickel and iron oxidation cases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c2cp40549kDOI Listing
May 2012

Evaluation of Bovine chemerin (RARRES2) Gene Variation on Beef Cattle Production Traits.

Front Genet 2012 29;3:39. Epub 2012 Mar 29.

U.S. Meat Animal Research Center, Agricultural Research Service, United States Department of Agriculture Clay Center, NE, USA.

A previous study in cattle based on >48,000 markers identified markers on chromosome 4 near the chemerin gene associated with average daily feed intake (ADFI) in steers (P < 0.008). Chemerin is an adipokine associated with obesity and metabolic syndrome in humans, representing a strong candidate gene potentially underlying the observed association. To evaluate whether the bovine chemerin gene is involved in feed intake, 16 markers within and around the gene were tested for association in the same resource population. Eleven were nominally significant for ADFI (P < 0.05) and two were significant after Bonferroni correction. Two and five SNP in this region were nominally significant for the related traits of average daily gain (ADG) and residual feed intake (RFI), respectively. All markers were evaluated for effects on meat quality and carcass phenotypes. Many of the markers associated with ADFI were associated with hot carcass weight (HCW), adjusted fat thickness (AFT), and marbling (P < 0.05). Marker alleles that were associated with lower ADFI were also associated with lower HCW, AFT, and marbling. Markers associated with ADFI were genotyped in a validation population of steers representing 14 breeds to determine predictive merit across populations. No consistent relationships for ADFI were detected. To determine whether cattle feed intake or growth phenotypes might be related to chemerin transcript abundance, the expression of chemerin was evaluated in adipose of 114 heifers that were siblings of the steers in the discovery population. Relative chemerin transcript abundance was not correlated with ADFI, ADG, or RFI, but associations with body condition score and yearling weight were observed. We conclude that variation in the chemerin gene may underlie observed association in the resource population, but that additional research is required to determine if this variation is widespread among breeds and to develop robust markers with predictive merit across breeds.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fgene.2012.00039DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3314841PMC
October 2012

Minimum detectable concentration as a function of gamma walkover survey technique.

Health Phys 2012 Feb;102 Suppl 1:S22-7

Oak Ridge Associated Universities, Independent Environmental Assessment and Verification, 1299 Bethel Valley Road, Oak Ridge, TN, USA.

Gamma walkover surveys are often performed by swinging the radiation detector (e.g., a 2-inch by 2-inch sodium iodide) in a serpentine pattern at a near constant height above the ground surface. The objective is to survey an approximate 1-m swath with 100% coverage producing an equal probability of detecting contamination at any point along the swing. In reality, however, the detector height will vary slightly along the swing path, and in some cases the detector may follow a pendulum-like motion significantly reducing the detector response and increasing the minimum detectable concentration. This paper quantifies relative detector responses for fixed and variable height swing patterns and demonstrates negative impacts on the minimum detectable concentration. Minimum detectable concentrations are calculated for multiple contaminated surface areas (0.1, 1.0, 3, 10, and 30 m2), multiple contaminants (60Co, 137Cs, 241Am, and 226Ra), and two minimum heights (5 and 10 cm). Exposure rate estimates used in minimum detectable concentration calculations are produced using MicroShield™ v.7.02 (Grove Software, Inc., 4925 Boonsboro Road #257, Lynchberg, VA 24503) and MDCs are calculated as outlined in NUREG-1575. Results confirm a pendulum-like detector motion can significantly increase MDCs relative to a low flat trajectory, especially for small areas of elevated activity--up to a 47% difference is observed under worst-modeled conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/HP.0b013e318237e757DOI Listing
February 2012

Conversion of mouse fibroblasts to sphere cells induced by AlbuMAXI-containing medium.

Front Biosci (Elite Ed) 2012 Jan 1;4:1813-22. Epub 2012 Jan 1.

Department of Biology, and Center for Tissue Regeneration and Engineering, University of Dayton, Dayton, Ohio 45469, USA.

The reprogramming of fibroblasts to pluripotent stem cells and the direct conversion of fibroblasts to functional neurons has been successfully manipulated by ectopic expression of defined factors. We demonstrate that mouse fibroblasts can be converted into sphere cells by detaching the fibroblast cells by protease and then using the AlbuMAX I-containing culture medium without genetic alteration. AlbuMAX I is a lipid-rich albumin. Albumin-associated lipids arachidonic acid (AA) and pluronic F-68 were responsible for this effect. The converted colonies were positive for both alkaline phosphatase and surface specific embryonic antigen-1 (SSEA-1) staining. Global gene expression analysis indicated that the sphere cells were in an intermediate state compared with mES cells and MEF cells. The sphere cells were able to differentiate into tissues representing all three embryonic germ layers following retinoic acid treatment, and differentiated into smooth muscle cells following treatment with vascular endothelial growth factor (VEGF). The study presented a potential novel approach to transdifferentiate mouse fibroblast cells into other cell lineages mediated by AlbuMAX I-containing culture medium.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2741/502DOI Listing
January 2012

Hydrogenation of N over Fe{111}.

Proc Natl Acad Sci U S A 2011 Jan 8;108(3):925-30. Epub 2010 Nov 8.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom.

Over the past five decades, ultra high vacuum (uhv) techniques applied to well-defined single-crystal samples (the "surface science paradigm") have transformed our understanding of fundamental surface chemistry. To translate this success to the world of realistic heterogeneous catalysis, however, requires one seriously to address the fact that real heterogeneous catalysts usually operate under near-ambient or higher pressures. Nevertheless, the surface science paradigm can undoubtedly provide crucial insights into catalytic processes, so long as care is exercised in the design of experiments. Forging a secure link between two radically different pressure regimes is the major challenge, which we illustrate here with reference to the vitally important ammonia synthesis reaction, achieved industrially only under extremely high pressure.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1006634107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3024688PMC
January 2011

Positive charge States and possible polymorphism of gold nanoclusters on reduced ceria.

J Am Chem Soc 2010 Feb;132(7):2175-82

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.

The catalytic properties of Au/CeO(2) systems are sensitive to the nature of Au clusters; however, atomic information on Au clusters is sparse. In this work, we use density functional theory to investigate the nucleation of small Au clusters (up to Au(11)). By depositing Au atoms one by one at a reduced CeO(2){111} surface, we present detailed nucleation patterns. Although relatively small in size, the nanoclusters obtained exhibit interesting characteristic features. In addition to the face-centered cubic (fcc) geometry, reminiscent of bulk Au, we also find the existence of novel hexagonal close-packed (hcp) structures. Furthermore, the facets of the nanoclusters are versatile, comprising {111}/{100} combinations for the fcc-like clusters and {10(1)1}/{0001} combinations for the hcp-like. Electronically, the contact layer Au atoms that bond with surface O atoms are positively charged, which could have significant implications in catalysis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/ja906687fDOI Listing
February 2010

Fischer-Tropsch synthesis of liquid fuels: learning lessons from homogeneous catalysis.

Phys Chem Chem Phys 2009 Dec 30;11(47):11110-2. Epub 2009 Sep 30.

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, UK CB2 1EW.

Herein, we present results opposing the so-called carbide mechanism in the Fischer-Tropsch synthesis of liquid fuels and point out analogies between this heterogeneously catalysed process and related homogeneous processes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/b915696hDOI Listing
December 2009

Dynamics of water adsorption on Pt{110}-(1x2): a molecular dynamics study.

J Chem Phys 2009 Aug;131(6):064703

Department of Chemistry, University of Cambridge, Lensfield Rd, CB2 1EW Cambridge, United Kingdom.

Recent experimental studies of water adsorption on Pt{110}-(1x2) using supersonic molecular beams [F. R. Laffir et al., J. Chem. Phys. 128, 114717 (2008)] have revealed that the translational energy dependence of the initial sticking probability is a stepwise function with a threshold energy of 5 kJ/mol. The initial sticking probability increases sixfold from approximately 0.1 (at translational energies less than 5 kJ/mol) to approximately 0.64 (at translational energies greater than 10 kJ/mol). The aim of this work is to study the adsorption dynamics of water using classical molecular dynamics simulation in order to assess what physical factors are responsible for the observed behavior of the initial sticking probability. The simulations were performed using a purpose-designed code; water molecules were modeled using the well-known TIP4P water model, whereas the water-platinum potential energy function was determined using the ab initio density functional theory calculations. We conclude that the main factor controlling the initial sticking probability is a relatively weak energy transfer between the water molecule and the surface substrate during collision. This energy transfer is enhanced when the total energy of the water molecule increases. The assumption of an exponential increase of the probability of the energy transfer as a function of total energy of water molecule gives initial sticking probabilities very similar to those experimentally obtained. The same model was applied for the simulation of the coverage dependent sticking probability using a hybrid method comprising molecular dynamics and kinetic Monte Carlo approaches. We found a reasonable agreement between our results and the experimental data. The sticking probability as a function of coverage initially increases due to an increasing amount of the adsorbate island edges; it reaches a maximum and finally decreases as the islands merge together at high coverage. The saturation coverage was determined to be 2.8 ML at surface temperature 165 K, where water forms a puckered almost regular lattice with each water molecule having four nearest neighbors. At the studied temperature we did not observe the existence of stable water multilayers on the surface which is consistent with the experimental findings.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.3204700DOI Listing
August 2009

Prevalence and enumeration of Escherichia coli O157:H7 and Salmonella in U.S. abattoirs that process fewer than 1000 head of cattle per day.

J Food Prot 2009 Jun;72(6):1272-8

U.S. Department of Agriculture, Agricultural Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska 68933-0166, USA.

A significant portion (15 to 20%) of beef in the United States is produced in small beef processing plants that harvest fewer than 1000 cattle per day. However, there are little data on the prevalence and levels of Escherichia coli O157:H7 and Salmonella in these processing plants. To address this lack of data, hides (n=1995) and carcasses (n=1995) of cattle at seven small processing plants located across the United States were analyzed for E. coli O157:H7 and Salmonella. Across all plants, hide prevalence of E. coli O157:H7 and Salmonella was 71 and 91%, respectively. Twelve percent of hides had E. coli O157:H7 at enumerable levels (> or =40 CFU/100 cm2), while 36% of hides had Salmonella at enumerable levels. Across all plants, the prevalence of E. coli O157:H7 on preevisceration carcasses was 33%, with 2% at an enumerable level (> or = 0.8 CFU/ 100 cm2). Across all plants, Salmonella prevalence on preevisceration carcasses was 58%, with 8% at an enumerable level. Significant plant-to-plant variations in levels and prevalence of pathogens on carcasses were detected. Reduced levels of pathogens on carcasses were noted among small processors that had incorporated a hide-directed intervention. The results obtained are comparable to those observed previously for larger processors, showing that smaller beef processors face and address the same challenges as do larger beef processors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4315/0362-028x-72.6.1272DOI Listing
June 2009