Al3+,Cr3+及Cd2+对日本三角涡虫摄食和运动行为的影响

以涡虫完全解体为死亡标准,在室温(26±1℃)下研究了Al3+,Cr3+及Cd2+分别对日本三角涡虫(Duge-sia japonica)的急性毒性,并运用图像分析技术对不同实验条件下三角涡虫的摄食和运动行为进行了定量分析.结果表明:在急性毒性实验处理96 h后,在cAl3+≥0.75 mmo/L,cCr3+≥0.2 mmol/L,cCd2+≥0.006 mmol/L时,涡虫全部死亡,且致死时间与药品浓度呈正相关;在cAl3+=0.15～0.65 mmol/L,cCr3+=0.05～0.15 mmol/L,cCd2+=0.002～0.005 mmol/L处理下均未有涡虫致死现象,但对涡虫的摄食和运动行为均有一定影响;随Al3+浓度的增高和处理时间的延长,实验组涡虫的活动范围和摄食率都降低;较低浓度的Cr3+对涡虫的运动和摄食行为具有促进作用,而较高浓度的Cr3+则有抑制作用;较低浓度的Cd2+对涡虫的运动和摄食率的影响不大,而较高浓度Cd2+实验组涡虫的爬行速度和摄食率均下降.     

Building multivariable prognostic and diagnostic models: transformation of the predictors by using fractional polynomials

To be useful to clinicians, prognostic and diagnostic indices must be derived from accurate models developed by using appropriate data sets. We show that fractional polynomials, which extend ordinary polynomials by including non-positive and fractional powers, may be used as the basis of such models. We describe how to fit fractional polynomials in several continuous covariates simultaneously, and we propose ways of ensuring that the resulting models are parsimonious and consistent with basic medical knowledge. The methods are applied to two breast cancer data sets, one from a prognostic factors study in patients with positive lymph nodes and the other from a study to diagnose malignant or benign tumours by using colour Doppler blood flow mapping. We investigate the problems of biased parameter estimates in the final model and overfitting using cross-validation calibration to estimate shrinkage factors. We adopt bootstrap resampling to assess model stability. We compare our new approach with conventional modelling methods which apply stepwise variables selection to categorized covariates. We conclude that fractional polynomial methodology can be very successful in generating simple and appropriate models.     

Making Milk and Money: Contemporary Mothers' Orientations to Breastfeeding and Work

In most Western industrial nations, gains have been made in women's educational and occupational opportunities as part of a larger gender revolution. At the same time, contemporary mothering expectations have expanded and intensified, especially the renewed focus on breastfeeding as the “optimal” choice for infant feeding. How do women perceive the simultaneous pursuit of these activities? Prior scholarship has identified tensions in cultural models of breastfeeding as well as in women's subjective experiences, emphasizing how breastfeeding is shaped and encountered through sociocultural context, especially ideologies that position work and mothering as incompatible. Building on this, I examine how the current generation of working mothers view working and breastfeeding. Through in‐depth interviews with 32 U.S. women, I show how women espouse distinctly different orientations to breastfeeding: instrumentalist, quasi‐maternalist, and pragmatist. I argue that these different orientations both reflect and reframe existing cultural models and discourses about contemporary women's relationships to work, mothering, and breastfeeding.     

Association between expressed breast milk feeding and breastfeeding duration in Hong Kong mothers

BackgroundExpressed breast milk feeding has increased substantially in the past two decades. Once used primarily for preterm infants, feeding expressed breast milk is now more common in mothers giving birth to healthy term infants. However, the effect of expressed breast milk feeding on breastfeeding duration is unclear.ObjectivesTo assess the association between breast milk expression practices and breastfeeding duration in women giving birth to healthy infants.MethodsFrom 2017 to 2018, we recruited 821 new mothers from two public hospitals in Hong Kong. Participants were followed up at 1.5, 3, and 6 months postpartum or until they stopped breastfeeding. The proportion, type, and mode of all milk feeding were assessed at each follow-up.ResultsAt 1.5 months postpartum, 47.9%, 37.7%, and 14.4% of participants were feeding by direct breastfeeding only, mixed-mode feeding, and expressed breast milk only, respectively. Participants feeding expressed breast milk only were more likely to be supplementing with infant formula. When compared with participants who provided only direct breastfeeding, participants who gave only expressed breast milk at 1.5 months had 57% lower odds of breastfeeding continuation at three months postpartum. After stratification by infant formula supplementation, expressed breast milk feeding only at 1.5 months was associated with an increased risk of breastfeeding cessation in participants supplementing with infant formula (adjusted hazard ratio [aHR] = 1.86, 95% CI = 1.17–2.95).ConclusionIn the first six months postpartum, giving only expressed breast milk is associated with early breastfeeding cessation, especially in participants who are also supplementing with infant formula.     

Impact of COVID-19 on breastfeeding intention and behaviour among postpartum women in five countries

BackgroundStudies regarding the impact of COVID-19 on breastfeeding have mostly used single- country samples or a qualitative design.AimThe objective of this study was to examine breastfeeding intention during pregnancy and breastfeeding behaviour among postpartum women in five countries during the COVID-19 pandemic and the associated factors.MethodsAn online questionnaire survey was conducted in Thailand, the United Kingdom, South Korea, Taiwan, and Brazil from July through November 2021. The study participants included 3253 mothers within six months of birth.FindingsAbout 90% of participants intended to breastfeed during pregnancy and 85.7% reported breastfeeding in the past 24 h. More than half reported their breastfeeding duration being as planned or longer despite COVID-19. Multivariate logistic regression models showed that being multiparous, ever tested COVID-19 positive, and having positive breastfeeding beliefs were associated with increased odds for intention to breastfeed during pregnancy. Lower maternal educational level, being primiparous, ever tested COVID-19 positive, and experiencing food insecurity were associated with decreased odds for breastfeeding duration being as planned or longer. Vaginal birth, currently working or on maternity leave, breastfeeding beliefs, breastfeeding support from spouse/partner/friend/relative, online support groups, and in-person or telephone contact with healthcare professionals were associated with increased odds for breastfeeding duration being as planned or longer.ConclusionBreastfeeding intention and behaviour remained high during the COVID-19 pandemic. Online support groups and telephone contact with health professionals were effective during the pandemic.     

Agreement Between Scales in the Measurement of Breast Cancer Risk Perceptions

The objective of this article is to compare the accuracy and numeric responses of breast cancer risk perception as measured by a frequency scale and percentage scale. A cross-sectional survey was conducted. Perceptions of five-year and lifetime breast cancer risk were measured using a frequency and a percentage scale. Estimation error was calculated as the absolute difference between actual breast cancer risk as determined by the Gail model and perceived risk. Agreement between scales was determined by calculating the mean and standard deviation of the difference between numeric responses. The study was conducted among women enrolled in two primary care clinics associated with an academic medical center. Two-hundred-fifty-four participants were recruited from one of the two participating internal medicine clinics. Inclusion criteria included female gender and age 40-84 years. Exclusion criteria included a history of breast cancer, dementia, or a life expectancy of less than two years. The frequency scale was more accurate than the percentage scale in estimating lifetime risk (p= 0.05), but less accurate in estimating five-year risk (p < 0.02). Only 79 participants (31%) were considered consistent scale users, providing identical responses when using the frequency and percentage scale for a given risk estimate. Although the mean difference (percentage-frequency scale) for estimates of breast cancer lifetime risk was only 2.4, the empirically determined 90% limits of agreement between the frequency and percentage scale for lifetime risk were wide, from -30 to 40. Higher numeracy was associated with consistent use of scales (OR 1.61, 95% CI; 1.09-2.37). We report disagreement in breast cancer risk perceptions when measured by a frequency and a percentage scale. The accuracy and direction of bias associated with each scale varies according to the time frame of risk being assessed.     

Early feeding problems: identification by parents and health care personnel

This study investigated the discrepancy between parental reports indicating a high prevalence of feeding problems during infancy and the relatively low identification rate of such cases at child health care centers. Thirty nurses were interviewed about definitions, prevalence, causes, and interventions for such problems. Thereafter, they were retrospectively asked about presence of feeding problems in 30 infants, for whom parents had reported existence of feeding problems, and in 30 control infants. A group ( n =22) based on parent-nurse agreement about the existence of a problem was compared with a group ( n = 8) identified as problematic by parents only and with the control group. The parent-nurse agreement group stood out as more burdened: infant growth was affected, there had been feeding history problems (breastfeeding, weaning and protracted meals) and the level of parental concern was higher. More infant respiratory infections were reported, and more medication had been prescribed for this group. Although nurses seemed to rely to a great extent on parental reports in identifying feeding problems, the present results suggested that the parent-nurse discrepancy in identification rate may occur due to nurses' weighting of parental complaints with other factors such as the child's general condition and the family social situation.     

蓄电池生产线极板上料装置

针对蓄电池生产线包封工序中存在大量手工上料,铅粉危害操作人健康,提出了极板自动上料的方案,分析比较 各方案的优缺点,设计了极板上料装置。极板上料装置投入运用后,解决了极板包片机上料的瓶颈,降低了工人劳动强 度,提高了劳动生产率     

我国生猪生产效率及补贴政策评价

文章采用数据包络分析方法（DEA）分别对我国生猪生产效率进行了区域差异和规模比较。研究表明,生猪生产效率呈现出明显的地区差异,与西部地区比较,东部更有效率,但呈现规模不经济的状况;规模养殖比散养有较高的经济效率,但散养生猪仍具有较灵活的成本优势。根据研究结论,认为中国实施区域差别化的生猪补贴扶持政策有一定的合理性,但应有侧重,东部应侧重效率导向,中西部地区应以规模导向为主;同时在发展规模化养殖过程中也应注意差异化,对不同规模养殖户实行差别的补贴政策;生猪补贴政策还应充分考虑生产和消费布局等。