Effects on soil carbon storage from municipal biosolids application to agricultural fields.

This study investigated the influence of biosolid applications on soil carbon storage and evaluated nutrient management strategies affecting soil carbon dynamics. The research assessed alterations in soil pH, soil carbon stock, and soil nitrogen content within short-term and long-term biosolids-amended soils in Bible Hill, Nova Scotia, Canada, extending to a depth of 0-60 cm. The findings indicated an increase in soil pH with alkaline treatment biosolids (ATB) applications across both study sites, with a legacy effect on soil pH noted in the long-term biosolids-amended soil following a single ATB application over 13 years. Both sites demonstrated significant increases in soil total carbon (STC) and soil organic carbon (SOC) within the 0-30 cm soil depth after biosolid application, and soil inorganic carbon (SIC) accounted for approximately 5-10% of STC, specifically in the surface soil layer (0-15 cm). In the long-term study site, annual 14, 28 and 42 Mg ATB ha-1 treatments resulted in a substantial rise in soil carbon stock (59.5, 60.1 and 68.0 Mg C ha-1), marking a 25% increase compared to control soil. The SOC content in biosolids-amended soil showed a declining trend with increasing soil depth at both study sites. Notably, the carbon stock in the short-term site was observed in composted biosolids (COMP) > ATB > liquid mesophilic anaerobically digested biosolids (LMAD) from the 0-60 cm soil depth. Approximately 79-80% of the variation in SOC response at both sites was concentrated within the top 30 cm soil. Soil total nitrogen (STN) showed no significant differences at the short-term site, and STN in biosolids-amended soil decreased with increasing soil depth at the long-term site. Biosolids-induced C retention coefficients (BCR) for ATB remained consistent at both sites, ranging from -13% to 31.4% with a mean of 11.12%. BCR values for COMP ranged from 1.9% to 34.4% with a mean of 18.73%, while those for LMAD exhibited variability, spanning from -6.2% to 106.3% with a mean of 53.9%.

Seasonal changes in the abundance and activity of bacterial and fungal denitrifying communities associated with different compost amendments.

Composts can be efficient organic amendments in potato culture as they can supply carbon and nutrients to the soil. However, more information is required on the effects of composts on denitrification and nitrous oxide emissions (N2O) and emission-producing denitrifying communities. The effects of three compost amendments (municipal source separated organic waste compost (SSOC), forestry waste mixed with poultry manure compost (FPMC), and forestry residues compost (FRC)) on fungal and bacterial denitrifying communities and activity was examined in an agricultural field cropped to potatoes during the fall, spring, and summer seasons. The denitrification enzyme activity (DEA), N2O emissions, and respiration were measured in parallel. N2O emission rates were greater in FRC-amended soils in the fall and summer, whereas soil respiration was highest in the SSOC-amended soil in the fall. A large number of nirK denitrifying fungal transcripts were detected in the fall, coinciding with compost application, while the greatest nirK bacterial transcripts were measured in the summer when plants were actively growing. Denitrifying community and transcript levels were poor predictors of DEA, N2O emissions, or respiration rates in compost-amended soil. Overall, the sampling date was driving the population and activity levels of the three denitrifying communities under study.

Pathogenic Streptomyces spp. Abundance Affected by Potato Cultivars.

Potato cultivars vary in their tolerance to common scab; however, how they affect common scab-causing Streptomyces spp. populations over time is poorly understood. This study investigated the effects of potato cultivar on pathogenic Streptomyces spp. abundance, measured using quantitative PCR, in three spatial locations in a common scab-infested field: (i) soil close to the plant (SCP); (ii) rhizosphere soil (RS); and (iii) geocaulosphere soil (GS). Two tolerant (Gold Rush, Hindenburg) and two susceptible cultivars (Green Mountain, Agria) were tested. The abundance of pathogenic Streptomyces spp. significantly increased in late August compared with other dates in RS of susceptible cultivars in both years. Abundance of pathogenic Streptomyces spp., when averaged over locations and time, was significantly greater in susceptible cultivars compared with tolerant cultivars in 2014. Principal coordinates analysis showed that SCP and RS soil properties (pH, organic carbon, and nitrogen concentrations) explained 68 and 76% of total variation in Streptomyces spp. abundance among cultivars in 2013, respectively, suggesting that cultivars influenced common scab pathogen growth conditions. The results suggested that the genetic background of potato cultivars influenced the abundance of pathogenic Streptomyces spp., with five to six times more abundant Streptomyces spp. in RS of susceptible cultivars compared with tolerant cultivars, which would result in substantially more inoculum left in the field after harvest.

Novel P450nor Gene Detection Assay Used To Characterize the Prevalence and Diversity of Soil Fungal Denitrifiers.

UNLABELLED: Denitrifying fungi produce nitrous oxide (N2O), a potent greenhouse gas, as they generally lack the ability to convert N2O to dinitrogen. Contrary to the case for bacterial denitrifiers, the prevalence and diversity of denitrifying fungi found in the environment are not well characterized. In this study, denitrifying fungi were isolated from various soil ecosystems, and novel PCR primers targeting the P450nor gene, encoding the enzyme responsible for the conversion of nitric oxide to N2O, were developed, validated, and used to study the diversity of cultivable fungal denitrifiers. This PCR assay was also used to detect P450nor genes directly from environmental soil samples. Fungal denitrification capabilities were further validated using an N2O gas detection assay and a PCR assay targeting the nirK gene. A collection of 492 facultative anaerobic fungi was isolated from 15 soil ecosystems and taxonomically identified by sequencing the internal transcribed spacer sequence. Twenty-seven fungal denitrifiers belonging to 10 genera had the P450nor and the nirK genes and produced N2O from nitrite. N2O production is reported in strains not commonly known as denitrifiers, such as Byssochlamys nivea, Volutella ciliata, Chloridium spp., and Trichocladium spp. The prevalence of fungal denitrifiers did not follow a soil ecosystem distribution; however, a higher diversity was observed in compost and agricultural soils. The phylogenetic trees constructed using partial P450nor and nirK gene sequences revealed that both genes clustered taxonomically closely related strains together. IMPORTANCE: A PCR assay targeting the P450nor gene involved in fungal denitrification was developed and validated. The newly developed P450nor primers were used on fungal DNA extracted from a collection of fungi isolated from various soil environments and on DNA directly extracted from soil. The results indicated that approximatively 25% of all isolated fungi possessed this gene and were able to convert nitrite to N2O. All soil samples from which denitrifying fungi were isolated also tested positive for the presence of P450nor The P450nor gene detection assay was reliable in detecting a large diversity of fungal denitrifiers. Due to the lack of homology existing between P450nor and bacterial denitrification genes, it is expected that this assay will become a tool of choice for studying fungal denitrifiers.

Tillage Management and Seasonal Effects on Denitrifier Community Abundance, Gene Expression and Structure over Winter.

Tillage effects on denitrifier communities and nitrous oxide (N2O) emissions were mainly studied during the growing season. There is limited information for the non-growing season, especially in northern countries where winter has prolonged periods with sub-zero temperatures. The abundance and structure of the denitrifier community, denitrification gene expression and N2O emissions in fields under long-term tillage regimes [no-tillage (NT) vs conventional tillage (CT)] were assessed during two consecutive winters. NT exerted a positive effect on nirK and nosZ denitrifier abundance in both winters compared to CT. Moreover, the two contrasting managements had an opposite influence on nirK and nirS RNA/DNA ratios. Tillage management resulted in different denitrifier community structures during both winters. Seasonal changes were observed in the abundance and the structure of denitrifiers. Interestingly, the RNA/DNA ratios were greater in the coldest months for nirK, nirS and nosZ. N2O emissions were not influenced by management but changed over time with two orders of magnitude increase in the coldest month of both winters. In winter of 2009-2010, emissions were mainly as N2O, whereas in 2010-2011, when soil temperatures were milder due to persistent snow cover, most emissions were as dinitrogen. Results indicated that tillage management during the growing season induced differences in denitrifier community structure that persisted during winter. However, management did not affect the active cold-adapted community structure.

Eating Disordered Behaviors and Body Disapproval in Adolescent Males Adjudicated for Sexual and Nonsexual Crimes.

Using a large sample of adjudicated delinquent male youth (N = 696), we compared data from youth who had been adjudicated for sexually aggressive crimes and those who had been adjudicated for nonsexual offenses on eating dysfunction, body disapproval, history of sexual abuse, and pornography exposure. The sample included 526 (75.8%) youth adjudicated for sexual offenses and 170 (24.4%) youth adjudicated for nonsexual crimes. The average age of the sample was 16.8 years (SD = 1.6), and approximately half of the sample (47.7%, n = 310) self-identified as White. The results of hierarchical multiple regressions indicated that sexually aggressive youth scored significantly higher than nonsexually offending youth on both eating dysfunction and body disapproval measures. Pornography exposure and substance use predicted body disapproval and eating dysfunction in the entire sample of adjudicated youth. History of sexual abuse was a significant predictor of body disapproval in all adjudicated youth but was not a significant predictor of eating dysfunction. Implications for research and practice are offered.

Emergence of nonsexual crimes and their relationship to sexual crime characteristics and the deviant arousal of male adolescent sexual offenders: an exploratory study.

In this study, we explore nonsexual crimes committed by a sample of 437 incarcerated adolescent sexual offenders as well as deviant arousal and its relationships to nonsexual and sexual crimes. Over 50% of the juvenile sexual offenders in this sample have committed nonsexual offenses. In addition, nonsexual crimes, particularly general delinquency, were significantly correlated to a number of characteristics of sexual crimes committed by the youth. Previous research has shown that sexually abusive youth are more likely to recidivate nonsexual crimes, and among the implications of this study is the need for treatment providers and service delivery systems to address nonsexual as well as sexual crimes.

Part II: differences between sexually victimized and nonsexually victimized male adolescent sexual abusers and delinquent youth: further group comparisons of developmental antecedents and behavioral challenges.

In a recent paper published in the Journal of Child Sexual Abuse, we assessed the differences between sexually victimized and nonsexually victimized male adolescent sexual abusers ( Burton, Duty, & Leibowitz, 2011 ). We found that the sexually victimized group had more severe developmental antecedents (e.g., trauma and early exposure to pornography) and behavioral difficulties (sexual aggression, arousal, pornography use, and nonsexual offenses). The present study compares sexually victimized and nonsexually victimized adolescent sexual abusers with a group of nonsexually victimized delinquent youth. Findings included that delinquent youth had fewer behavioral and developmental problems than the comparison groups. In addition, sexually victimized sexual abusers had the highest mean scores on trauma and personality measures. Implications for research and treatment are offered.

Chemical fumigation and biofumigation alter soil bacterial community diversity and composition.

Chemical fumigation and biofumigation are used to reduce soil-borne diseases in agricultural production systems; however, non-targeted soil microorganisms may also be affected. This study compared the effects of chemical fumigation, either used alone or combined with an organic amendment, and biofumigation on soil bacterial community diversity and composition under controlled conditions over 160 days. Treatments included: fumigation with chloropicrin (CP), fumigation with metam sodium used alone (MS) or combined with barley plant residues (MSBR); biofumigation with mustard plant residues; addition of barley plant residues; and untreated control. Biofumigation had a greater impact on bacterial diversity at early time points, transiently decreasing species evenness and yielding the most dissimilar ß-diversity after 3 days. MS fumigation did not affect bacterial diversity indices; however, MSBR transiently decreased species evenness after 8 days. CP-treated soil had decreased species evenness that did not recover over time and had the most dissimilar ß-diversity at the end of the incubation compared to all other treatments. This study demonstrated that CP fumigation had the greatest and most persistent impact on bacterial diversity, whereas MS fumigation and biofumigation led to transient decreases in bacterial diversity.

Effect of nitrate and glucose addition on denitrification and nitric oxide reductase (cnorB) gene abundance and mRNA levels in Pseudomonas mandelii inoculated into anoxic soil.

The effect of glucose addition (0 and 500 µg C g(-1) soil) and nitrate (NO(3)) addition (0, 10, 50 and 500 µg NO(3)-N g(-1) soil) on nitric oxide reductase (cnorB) gene abundance and mRNA levels, and cumulative denitrification were quantified over 48 h in anoxic soils inoculated with Pseudomonas mandelii. Addition of glucose-C significantly increased cnorB(p) (P. mandelii and related species) mRNA levels and abundance compared with soil with no glucose added, averaged over time and NO(3) addition treatments. Without glucose addition, cnorB(p) mRNA levels were higher when 500 µg NO(3)-N g(-1) soil was added compared with other NO(3) additions. In treatments with glucose added, addition of 50 µg NO(3)-N g(-1) soil resulted in higher cnorB(p) mRNA levels than soil without NO(3) but was not different from the 10 and 500 µg NO(3)-N g(-1) treatments. cnorB(p) abundance in soils without glucose addition was significantly higher in soils with 500 µg NO(3)-N g(-1) soil compared to lower N-treated soils. Conversely, addition of 500 µg NO(3)-N g(-1) soil resulted in lower cnorB(p) abundance compared with soil without N-addition. Over 48 h, cumulative denitrification in soils with 500 µg glucose-C g(-1) soil, and 50 or 500 µg NO(3)-N g(-1) was higher than all other treatments. There was a positive correlation between cnorB(p) abundance and cumulative denitrification, but only in soils without glucose addition. Glucose-treated soils generally had higher cnorB(p) abundance and mRNA levels than soils without glucose added, however response of cnorB(p) abundance and mRNA levels to NO(3) supply depended on carbon availability.

Exploring the relationships between dissociation, victimization, and juvenile sexual offending.

An etiological model of sexually abusive behavior including dissociation could have utility for researchers and treatment providers working with sexually abusive youth with trauma histories. This article explores relationships between dissociation, victimization, and juvenile sexual offending. Self-reported data on dissociation and 5 types of abuse were collected from 2 racially/ethnically diverse groups of sexually abusive and general delinquent male adolescents (n = 502). Bivariate analysis showed significant correlations between all types of child abuse and dissociation with the exception of emotional neglect. Hierarchical logistic regression analysis indicated that dissociation was significant in predicting sexual offender status. Moreover, dissociation, sexual victimization, and physical abuse showed significant effects in predicting membership in the sexual offender group. The results confirm the need for additional research in the areas of assessment and treatment of dissociation among sexually abusive youth.

Differences between sexually victimized and nonsexually victimized male adolescent sexual abusers: developmental antecedents and behavioral comparisons.

This study compares sexually victimized and nonsexually victimized male adolescent sexual abusers on a number of variables. Self-report measures were administered to 325 male sexually abusive youth (average age 16) in six residential facilities in the Midwest, 55% of whom reported sexual victimization. The results indicate that the sexually victimized sexual abusers have more severe developmental antecedents (trauma, family characteristics, early exposure to pornography and personality) and recent behavioral difficulties (characteristics of sexual aggression, sexual arousal, use of pornography, and nonsexual criminal behavior) than the nonsexually victimized group. Results are contrasted with recent typological research, which found no relationship between sexual victimization and subtype membership. Treatment, research, and theoretical implications are discussed.

Changes in denitrifier abundance, denitrification gene mRNA levels, nitrous oxide emissions, and denitrification in anoxic soil microcosms amended with glucose and plant residues.

In agricultural cropping systems, crop residues are sources of organic carbon (C), an important factor influencing denitrification. The effects of red clover, soybean, and barley plant residues and of glucose on denitrifier abundance, denitrification gene mRNA levels, nitrous oxide (N(2)O) emissions, and denitrification rates were quantified in anoxic soil microcosms for 72 h. nosZ gene abundances and mRNA levels significantly increased in response to all organic carbon treatments over time. In contrast, the abundance and mRNA levels of Pseudomonas mandelii and closely related species (nirS(P)) increased only in glucose-amended soil: the nirS(P) guild abundance increased 5-fold over the 72-h incubation period (P < 0.001), while the mRNA level significantly increased more than 15-fold at 12 h (P < 0.001) and then subsequently decreased. The nosZ gene abundance was greater in plant residue-amended soil than in glucose-amended soil. Although plant residue carbon-to-nitrogen (C:N) ratios varied from 15:1 to 30:1, nosZ gene and mRNA levels were not significantly different among plant residue treatments, with an average of 3.5 x 10(7) gene copies and 6.9 x 10(7) transcripts g(-1) dry soil. Cumulative N(2)O emissions and denitrification rates increased over 72 h in both glucose- and plant-tissue-C-treated soil. The nirS(P) and nosZ communities responded differently to glucose and plant residue amendments. However, the targeted denitrifier communities responded similarly to the different plant residues under the conditions tested despite changes in the quality of organic C and different C:N ratios.

Exploring the overlap in male juvenile sexual offending and general delinquency: trauma, alcohol use, and masculine beliefs.

Despite Burton and Meezan's (2004) finding that sexually aggressive youth are three to four times more likely to recidivate nonsexually than sexually, there is little to no research to date that explores this overlap in criminality. With a sample of 290 male sexually violent adjudicated and incarcerated youth, this study was able to successfully predict those who are exclusively sexually violent from those who are both nonsexually and sexually violent with each of the following factors: childhood trauma, masculine beliefs, and alcohol use. While alcohol use accounted for the greatest variance between the groups, masculine beliefs offered the greatest basis for the discussion and future projects for the authors of the study. Treatment and research implications are offered.

Effect of nitrate and acetylene on nirS, cnorB, and nosZ expression and denitrification activity in Pseudomonas mandelii.

Nitrate acts as an electron acceptor in the denitrification process. The effect of nitrate in the range of 0 to 1,000 mg/liter on Pseudomonas mandelii nirS, cnorB, and nosZ gene expression was studied, using quantitative reverse transcription-quantitative PCR. Denitrification activity was measured by using the acetylene blockage method and gas chromatography. The effect of acetylene on gene expression was assessed by comparing denitrification gene expression in P. mandelii culture grown in the presence or absence of acetylene. The higher the amount of NO(3)(-) present, the greater the induction and the longer the denitrification genes remained expressed. nirS gene expression reached a maximum at 2, 4, 4, and 6 h in cultures grown in the presence of 0, 10, 100, and 1,000 mg of KNO(3)/liter, respectively, while induction of nirS gene ranged from 12- to 225-fold compared to time zero. cnorB gene expression also followed a similar trend. nosZ gene expression did not respond to NO(3)(-) treatment under the conditions tested. Acetylene decreased nosZ gene expression but did not affect nirS or cnorB gene expression. These results showed that nirS and cnorB responded to nitrate concentrations; however, significant denitrification activity was only observed in culture with 1,000 mg of KNO(3)/liter, indicating that there was no relationship between gene expression and denitrification activity under the conditions tested.

Effect of pH and temperature on denitrification gene expression and activity in Pseudomonas mandelii.

Pseudomonas mandelii liquid cultures were studied to determine the effect of pH and temperature on denitrification gene expression, which was quantified by quantitative reverse transcription-PCR. Denitrification was measured by the accumulation of nitrous oxide (N(2)O) in the headspace in the presence of acetylene. Levels of gene expression of nirS and cnorB at pH 5 were 539-fold and 6,190-fold lower, respectively, than the levels of gene expression for cells grown at pH 6, 7, and 8 between 4 h and 8 h. Cumulative denitrification levels were 28 micromol, 63 micromol, and 22 micromol at pH 6, 7, and 8, respectively, at 8 h, whereas negligible denitrification was measured at pH 5. P. mandelii cells grown at 20 degrees C and 30 degrees C exhibited 9-fold and 94-fold increases in levels of cnorB expression between 0 h and 2 h, respectively, and an average 17-fold increase in levels of nirS gene expression. In contrast, induction of cnorB and nirS gene expression for P. mandelii cells grown at 10 degrees C did not occur in the first 4 h. Levels of cumulative denitrification at 10 h were 6.6 micromol for P. mandelii cells grown at 10 degrees C and 20 degrees C and 30 micromol for cells grown at 30 degrees C. Overall, levels of cnorB and nirS expression were relatively insensitive to pH values over the range of pH 6 to 8 but were substantially reduced at pH 5, whereas gene expression was sensitive to temperature, with induction and time to achieve maximum gene expression delayed as the temperature decreased from 30 degrees C. Low pH and temperature negatively affected denitrification activity.

Linking changes in snow cover with microbial nitrogen cycling functional gene abundance and expression in agricultural soil.

In eastern Canada, climate change-related warming and increased precipitation may alter winter snow cover, with potential consequences for soil conditions, nitrogen (N) cycling, and microbes. We conducted a 2-year field study aimed at determining the influence of snow removal, snow accumulation, and ambient snow in a potato-barley crop system on the abundance and expression of denitrifier (nirS, nirK, nosZ) and nitrifier (ammonium oxidizing archaeal (AOA) and bacterial (AOB) amoA) genes. Denitrifier and nitrifier abundance and expression results were compared to N2O production, soil atmosphere accumulation, and surface fluxes. In the first winter, nirK abundance was lowest while AOB abundance was greatest in snow accumulation treatments. In the second winter, greatest abundances were observed in the ambient snow treatment, which had greatest N2O accumulation and spring thaw fluxes, suggesting a link between microbial populations and biogeochemical functioning. Treatment effects on gene expression were limited, but greatest AOA, AOB, and nosZ expression was measured near 0°C and above 15°C, indicating that activity was promoted by freeze-thaw conditions and at summer temperatures. Overall, effects of changing snow depth on denitrifier and nitrifier abundance were not solely due to change in soil temperature, but also to soil moisture and/or interactions between these parameters.

Nitric oxide reductase gene expression and nitrous oxide production in nitrate-grown Pseudomonas mandelii.

Pure cultures of Pseudomonas mandelii were incubated with or without nitrate, which acts as a substrate and an electron acceptor for denitrification. Nitric oxide reductase (cnorB) gene expression was measured using a quantitative reverse transcription-PCR, and nitrous oxide emissions were measured by gas chromatography. P. mandelii cells in either the presence or absence of nitrate demonstrated an increase in cnorB gene expression during the first 3 h of growth. The level of expression of cnorB in nitrate-amended cells remained high (average, 2.06 x 10(8) transcripts/microg of RNA), while in untreated cells it decreased to an average of 3.63 x 10(6) transcripts/microg of RNA from 4 to 6 h. Nitrous oxide accumulation in the headspace was detected at 2 h, and cumulative emissions continued to increase over a 24-h period to 101 mumol in nitrate-amended cells. P. mandelii cnorB gene expression was not detected under aerobic conditions. These results demonstrate that P. mandelii cnorB gene expression was induced 203-fold at 4 h when nitrate was present in the medium. Accumulations of N(2)O indicated that the cNorB enzyme was synthesized and active.

Changes in bacterial denitrifier community abundance over time in an agricultural field and their relationship with denitrification activity.

This study measured total bacterial and denitrifier community abundances over time in an agricultural soil cropped to potatoes (Solanum tuberosum L.) by using quantitative PCR. Samples were collected on 10 dates from spring to autumn and from three spatial locations: in the potato "hill" between plants (H), close to the plant (H(p)), and in the "furrow" (F). The denitrification rates, N(2)O emissions, and environmental parameters were also measured. Changes in denitrifier abundance over time and spatial location were small (1.7- to 2.7-fold for the nirK, nosZ, and cnorB(B) guilds), whereas the cnorB(P) community (Pseudomonas mandelii and closely related spp.) showed an approximately 4.6-fold change. The seasonal patterns of denitrifier gene numbers varied with the specific community: lower nosZ gene numbers in April and May than in June and July, higher cnorB(P) gene numbers in May and June than in March and April and September and November, higher nirK gene numbers in early spring than in late autumn, and no change in cnorB(B) gene numbers. Gene numbers were higher for the H(p) than the H location for the nosZ and nirK communities and for the cnorB(P) community on individual dates, presumably indicating an effect of the plant on denitrifier abundance. Higher cnorB(P) gene numbers for the H location than the F location and for nosZ and cnorB(B) on individual dates reflect the effect of spatial location on abundance. Denitrifier abundance changes were not related to any environmental parameter, although a weak relationship exists between cnorB(P) gene numbers, extractable organic carbon values, and temperature. Denitrification and N(2)O emissions were mostly regulated by inorganic nitrogen availability and water-filled pore space but were uncoupled from denitrifier community abundances measured in this system.

A social learning theory comparison of the sexual victimization of adolescent sexual offenders and nonsexual offending male delinquents.

OBJECTIVE: This paper tests hypotheses based on Garland and Dougher's (1990) formulation of the "victim to victimizer" relationship which is a social learning theory etiological approach to adolescent sexual offending. METHOD: Two hundred sixteen adolescent sexually victimized sexual offenders and 93 adolescent sexually victimized nonsexual offending delinquents from three Michigan sexual offender treatment facilities participated in an anonymous cross-sectional survey regarding their sexual victimization and offending as well as a social desirability measure. RESULTS: When comparing the two groups, nonsexually offending delinquents and sexually offending delinquents, the latter were found to have: closer relationships with their perpetrators; a higher chance of having a male perpetrator(s); a longer duration of sexual victimization; more forceful sexual victimization; and the experience of penetration as part of their sexual victimization. Logistic regression showed that the gender of the perpetrators being both male and female and the forcefulness of the perpetrators were the best predictors of being in the sexual offender group. CONCLUSIONS: The social learning theory hypotheses were generally supported. Further multivariate research on this theory is warranted.