Other-Sex Friendships in Late Adolescence: Risky Associations for Substance Use and Sexual Debut?

Adolescents’ friendships with other-sex peers serve important developmental functions, but they may also facilitate engagement in problem behavior. This study examines the unique contributions of other-sex friendships and friends’ behavior to alcohol use, smoking, and initiation of sexual intercourse among late adolescent girls and boys. A total of 320 adolescents (53% girls; 33% racial/ethnic minorities) provided sociometric nominations of friendships annually in grades 10–12. Friendship networks were derived using social network analysis in each grade. Adolescents and their friends also reported on their alcohol use, smoking, and sexual debut at each assessment. After controlling for demographics, previous problem behavior, and friends’ behavior, other-sex friendships in 10th grade were associated with initiation of smoking among girls over the following year, and other-sex friendships in 11th grade were linked with lower levels of subsequent alcohol use among boys. Additionally, friends’ smoking and sexual experience in 10th grade predicted the same behaviors for all adolescents over the following year. Other-sex friendships thus appear to serve as a risk context for adolescent girls’ smoking and a protective context for adolescent boys’ drinking. Promoting mixed-gender activities and friendships among older high school students may be helpful in reducing males’ alcohol use, but may need to incorporate additional components to prevent increases in females’ smoking

Dynamic networks and behavior: separating selection from influence.

A current problem in the analysis of behavioral dynamics, given a simultaneously evolving social network, is the difficulty of separating effects of partner selection from effects of social influence. In this paper we present a recently developed family of statistical models that enables researchers to separate the two effects in a statistically adequate manner. To illustrate our method we make use of a three-wave panel measured in the years 1995-1997 at a school in the West of Scotland. We are able to assess the strength of selection and influence mechanisms associated with friendship networks of substance-using adolescents

A Prospective Study of Adolescents' Peer Support: Gender Differences and the Influence of Parental Relationships

This longitudinal study investigates parent and child predictors of adolescents' perceived social support from peers. Adolescents (285) and their parents filled out surveys when students were 11 and 15 years of age. Parent reports of their own social support and child reports of parental support to them, depression, and self-esteem were used as predictors of adolescents' peer social support. Path analyses revealed functional dissimilarity in the predictive model, for boys and girls. For boys and girls, the amount of spousal support parents' reported impacted the amount of parent to child support that children reported. For boys, this relationship impacted their perceptions of peer support indirectly through depression. However, for girls, parents' own supportive relationships directly impacted both their self-esteem and depression, above and beyond parent to child support, which then impacted girls' peer social support.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45288/1/10964_2004_Article_229992.pd

INFLUENCE OF PACKAGING CONDITIONS ON SOME MICROBIAL PROPERTIES OF MINCED BEEF MEAT AT 4 degrees C STORAGE

WOS: 000299494200012In this study, the effect of initial head-spaces of atmospheric air, vacuum packaging and modified atmospheres packaging (MAP) containing 70% CO(2)/30% O(2) (MAP1); 50% O(2)/50% CO(2) (MAP2); 30% CO(2)/70% O(2) (MAP3); 50% O(2)/30% CO(2)/20% N(2) (MAP4); 30% O(2)/30% CO(2)/40% N(2) (MAPS) on some microbiological quality of minced beef meat stored at 4 degrees C were investigated with pH changes in time intervals (1, 3, 5, 7, 9, 11 and 14 d). At the results, total viable counts were different significantly (P 0.05) for total viable counts and psychrotrophs counts

Influence of packaging conditions on some microbial properties of minced beef meat at 4°C storage

In this study, the effect of initial head-spaces of atmospheric air, vacuum packaging and modified atmospheres packaging (MAP) containing 70% CO 2/30% O 2 (MAP1); 50% O 2/50% CO 2 (MAP2); 30% CO2/70% O 2 (MAP3); 50% O 2/30% CO2/20% N 2 (MAP4); 30% O 2/ 30% CO 2 /40% N 2 (MAP5) on some microbiological quality of minced beef meat stored at 4 °C were investigated with pH changes in time intervals (1, 3, 5, 7, 9, 11 and 14 d). At the results, total viable counts were different significantly (P < 0.01) for packaged with MAP2. Psychrotrophs, yeasts and molds counts were smaller for packaged with MAP1 than the others, packaging with MAP5 and MAP4 were also different significantly (P < 0.01) from the other samples for inhibiting coliform counts. Vacuum packaging was not different significantly (P > 0.05) for total viable counts and psychrotrophs counts

An evaluation of seed spacing accuracy of a vacuum type precision metering unit based on theoretical considerations and experiments [Teorik ve deneysel verilere dayali{dotless} olarak vakumlu tek dane ekim ünitesinin tohum arali{dotless}gi{dotless} düzgünlügünün degerlendirilmesi]

Currently the most widely used machine for precision seeding of cotton and maize seed is vacuum type. The capture of seeds by vacuum plate and the release of seeds from the vacuum plate should be performed precisely without missing or doubling. The physical phenomena should be clarified theoretically to understand how the precision seeding mechanism works. To solve these problems, an attempt was made to develop a nomogram using equations describing the technical characteristics of the seeder used in this study and to describe the seed capture mechanism relying on basic principles of fluid mechanics and aerodynamic properties of seeds. Seed spacing accuracy tests were performed to test the theory on a sticky belt in the laboratory. Quality of feed index, miss and multiple indices, and precision have been taken as a set of criteria for seed spacing accuracy. The regression models developed using the data obtained via sticky band tests showed that 16 seeds s-1 was the upper limit of seed release frequency (SRF) for cotton and maize seeds. The upper limit of vacuum plate peripheral speed was found to be 0.34 m s-1. The use of 72 holes instead of 26 holes in the vacuum plate at 6.3 kPa created a vacuum band in the width of 10 mm around holes and this increased the multiple index and caused a reduction in seeding performance. For this reason, the use of vacuum plates with 60 or 52 holes is recommended for cotton seed. The forward speed of either 1.0 or 1.5 m s-1 was found to be acceptable for the seed spacing of 0.05 and 0.10 m, respectively. Aerodynamic calculations verified that widely used vacuum plates with 26 holes were the appropriate ones for seeding maize seeds. The performance indices, namely the quality of feed, and miss and multiple indices, reduced significantly for cotton and maize seeding when the precision metering unit was run at 20% (11°) slope to the right as compared to the no slope condition. © TÜBİTAK

Development of a software to determine the emitter characteristics and the optimum length of new designed drip irrigation laterals

An appropriate design of a drip irrigation system in order to increase the uniformity of water distribution with a high efficiency is of importance. The first step for the design is the determination of suitable length of laterals. In order to do this, the emitter characteristics and the friction losses of new designed laterals on which the emitters are placed must be known by laboratory experiments. On the other hand, mathematical models developed can also be used for the determination of friction losses in drip irrigation laterals. In this study, a software in Visual Basic 6.0 programming language was developed and it helps analyzing the data from a new designed emitter in order to find out the main characteristics and friction losses and to obtain the optimum lateral length of the lateral in the shortest time with an acceptable accuracy in. The software included several options for the selection of in-line or on-line emitter type, pressure compensating or non-pressure compensating emitters. The software calculates the optimum lateral length based on the measurement and model equations and utilizes the step by step procedure. Optimum lateral length criterias in the software such as C u and q var for non-pressure compensating emitter and lateral end pressure for compensating emitter were used. The comparison of optimum lateral lengths indicated a very good agreement between the experimentally obtained results and the results from the use of mathematical models for different criteria and different slope conditions. The differences in optimum lateral lengths between the experimental and calculated values obtained from the mathematical models ranged between -0.4 and 0.7%. © Association for Scientific Research

Development of a mathematical model to predict head losses from disc filters in drip irrigation systems using dimensional analysis

A model was developed using dimensional analysis to predict head losses in disc filters. Three different filter designs, each with four different inlet and outlet pipe diameters, were used to measure head losses at different flow rates in the laboratory. The parameters influencing head losses were considered to be the inside diameters of the inlet and outlet pipes, the inside diameter of the filter body, the inflow and outflow area where the inlet and the outlet pipes intersect with the body of the filter, the, effective length of filter disc group, the outside and inside diameter of the filter disc, the water velocity in the inlet pipe and the kinematic viscosity of water. A dimensional analysis was carried out using Buckingham's pi-theorem. To develop the model, experimental head loss data from 12 filters were considered. The model accounted for 90.18% of the variation in the pressure coefficient. A comparison between the predicted and the measured head losses was in close agreement with a correlation coefficient of 99.5%. The results showed that the model may be used to determine head losses in disc filters with an acceptable accuracy if the variables are within the following ranges; inside diameters of inlet and outlet pipe 52.5-102.3 mm; inside diameter of filter body 155-210 mm; effective length of disc group 231-545 mm, inside diameter of filter disc 105-128 mm; outside diameter of filter disc 129-164 mm; inflow area where the inlet pipe intersects with the body of the filter 2240-16430 mm 2; outflow area where the outlet pipe intersects with the body of the filter 2160-9480 mm 2; flow rate 4.50-73.43 m 3h -1; and Reynolds number 19,005-361,310. © 2008 IAgrE

Optimization of the seed spacing uniformity performance of a precision seeder using spherical materials and response surface methodology

The objective of this study was to optimize the seed spacing uniformity performance of a precision seeder using spherical materials and Response Surface Methodology (RSM) and to verify the optimum levels of the variables. The variables considered in the study included vacuum on seed plate, the diameter of seed holes and peripheral speed of the seed plate. Spherical materials made of plastic were used and experiments based on Central Composite Design (CCD), one of the designs in RSM were carried out in the laboratory. The data obtained were divided into three different groups in order to obtain the values of Multiple Index, Quality of Feed Index, Miss Index. Other performance indicators called root mean square deviation and CP3 were also calculated and evaluated in the study. Prediction functions mostly for quality of feed index in polynomial form allowed the calculation of the optimum level of each independent variable. Optimum levels of the variables obtained for each spherical material were tested and verified