STEM graduates and secondary school curriculum: does early exposure to science matter?

Increasing the number of Science, Technology, Engineering and Math (STEM) university graduates is considered a key element for long-term productivity and competitiveness in the global economy. Still, little is known about what actually drives and shapes students' choices. This paper focusses on secondary school students at the very top of the ability distribution and explores the effect of more exposure to science on enrolment and persistence in STEM degrees at the university and on the quality of the university attended. The paper overcomes the standard endogeneity problems by exploiting the different timing in the implementation of a reform that induced secondary schools in the UK to offer more science to high ability 14 year-old children. Taking more science in secondary school increases the probability of enrolling in a STEM degree by 1.5 percentage point and the probability of graduating in these degrees by 3 percentage points. The results mask substantial gender heterogeneity: while girls are as willing as boys to take advanced science in secondary school - when offered -, the effect on STEM degrees is entirely driven by boys. Girls are induced to choose more challenging subjects, but still the most female-dominated ones

Parents, schools and human capital differences across countries

Results from international standardized tests show large cross-country differences in students’ performances. Where do these gaps come from? This paper argues that differences in cultural environments and parental inputs may be of great importance. We show that the school performance of second generation immigrants is closely related with the one of native students in their parents’ countries of origin. This holds true even after accounting for different family background characteristics, schools attended and selection into immigration. We quantify the overall contribution of various parental inputs to the observed cross-country differences in the PISA test performance, and show that they account for about 40% of the gap between East Asia and other regions. This pattern questions whether PISA scores should be interpreted only as a quality measure for a country’s educational system. They actually contain an important intergenerational and cultural component

Multitask agents and incentives: the case of teachingand research for university professors

This paper evaluates the behavioural responses of multitask agents to the provision of incentives skewed towards one task only. In particular it studies the case of strong research incentives for university professors and it analyzes their effects on the way university faculty members allocate effort between teaching and quantity and quality of research and on the way they select into different types of universities. I first obtain different individual level measures of teaching and research performance. Then, I estimate a difference in difference model, exploiting a natural experiment that took place at Bocconi University, which heavily strengthened incentives towards research in 2005. I find evidence that teaching and research efforts are substitutable in the professors' cost function: the impact of research incentives is positive on research activity and negative on teaching performance. The effects are driven by career concerns rather than by the monetary incentives and are stronger for low ability researchers. Moreover, under the new incentive regime lower ability researchers tend to leave the university. Since I estimate that teaching and research ability are positively correlated, this implies that also bad teachers tend to leave the university. These results are consistent with a model of incentives where agents allocate effort between two substitute tasks and ability is multidimensional

Essays in economics of education

This thesis studies aspects related to the role of schools characteristics and their governance on students’ learning outcomes. The thesis contains three chapters. The first chapter explores the effect of exposing students to more science in high school on their enrolment and persistence in STEM majors at university. It exploits the different timing in the implementation of a reform that induced high schools in the UK to offer more science to high ability 14 year-old children. The findings show that a stronger science curriculum at high school increases the probability of enrolling and of graduating in a STEM major at university. Moreover, the effect masks substantial gender heterogeneity. It is indeed mostly concentrated on boys. Girls tend to choose more scientific subjects, but still the most female-dominated ones: they choose medicine, not engineering. The second chapter of this thesis analyses the effects of providing strong research incentives to university professors on the way they allocate effort between teaching and research and on the way they select into different types of universities. I find evidence that teaching and research efforts are substitute in the professors’ cost function: the impact of research incentives is positive on research activity and negative on teaching performance. Effects are stronger for young faculty members, who are exposed not only to monetary incentives but also to career concerns. Moreover, I find that less skilled researchers tend to leave the university under stronger research incentives. Since I estimate that teaching and research skills are positively correlated, this implies that also bad teachers tend to leave the university. The overall impact of stronger research incentives on the university teaching quality is therefore ambiguous: the negative effect on teaching performance for incumbent professors is compensated by the positive sorting effect, given by changes in the composition of teachers. The third chapter explores where do the large cross-country differences in students’ performances in international standardized tests come from. This chapter argues that, while most of the debate concentrates on country differences in the school systems, differences in cultural environments and parental inputs are instead of great importance. I show indeed that the school performance of second generation immigrants is closely related to the average one of native students who still study in their parents’ countries of origin. This holds true even after accounting for different family background characteristics, different schools attended and different patterns of selection into immigration. This pattern questions whether PISA scores should be interpreted only as a quality measure for a country’s educational system. They actually contain an important intergenerational and cultural component. Parental inputs are found indeed to explain a large part of the cross country variation in school performance, for instance they account for more than one third of the gap between East Asia and other regions

Parents, schools and human capital differences across countries

This paper studies the contribution of parental influence in accounting for cross-country gaps in human capital achievements. We argue that the cross-country variation in unobserved parental characteristics is at least as important as the one in commonly used observable proxies of parental socio-economic background. We infer this through an indirect empirical approach, based on the comparison of the school performance of second generation immigrants. We document that, within the same host country or even the same school, students whose parents come from high-scoring countries in the PISA test do better than their peers with similar socioeconomic backgrounds. Differential selection into emigration does not explain this finding. The result is larger when parents have little education and have recently emigrated, suggesting the importance of country-specific cultural traits that parents progressively lose as they integrate in the new host country, rather than of an intergenerational transmission of education quality. Unobserved parental characteristics account for about 15% of the cross-country variance in test scores, roughly doubling the overall contribution of parental influence

Evaluation of plan complexity and dosimetric plan quality of total marrow and lymphoid irradiation using volumetric modulated arc therapy

PurposeTo assess the impact of the planner's experience and optimization algorithm on the plan quality and complexity of total marrow and lymphoid irradiation (TMLI) delivered by means of volumetric modulated arc therapy (VMAT) over 2010-2022 at our institute. MethodsEighty-two consecutive TMLI plans were considered. Three complexity indices were computed to characterize the plans in terms of leaf gap size, irregularity of beam apertures, and modulation complexity. Dosimetric points of the target volume (D2%) and organs at risk (OAR) (Dmean) were automatically extracted to combine them with plan complexity and obtain a global quality score (GQS). The analysis was stratified based on the different optimization algorithms used over the years, including a knowledge-based (KB) model. Patient-specific quality assurance (QA) using Portal Dosimetry was performed retrospectively, and the gamma agreement index (GAI) was investigated in conjunction with plan complexity. ResultsPlan complexity significantly reduced over the years (r = -0.50, p < 0.01). Significant differences in plan complexity and plan dosimetric quality among the different algorithms were observed. Moreover, the KB model allowed to achieve significantly better dosimetric results to the OARs. The plan quality remained similar or even improved during the years and when moving to a newer algorithm, with GQS increasing from 0.019 +/- 0.002 to 0.025 +/- 0.003 (p < 0.01). The significant correlation between GQS and time (r = 0.33, p = 0.01) indicated that the planner's experience was relevant to improve the plan quality of TMLI plans. Significant correlations between the GAI and the complexity metrics (r = -0.71, p < 0.01) were also found. ConclusionBoth the planner's experience and algorithm version are crucial to achieve an optimal plan quality in TMLI plans. Thus, the impact of the optimization algorithm should be carefully evaluated when a new algorithm is introduced and in system upgrades. Knowledge-based strategies can be useful to increase standardization and improve plan quality of TMLI treatments

Assessing the antitumor potential of variants of the extracellular carbohydrate polymer from synechocystis ΔsigF mutant

Cancer is a leading cause of death worldwide with a huge societal and economic impact. Clinically effective and less expensive anticancer agents derived from natural sources can help to overcome limitations and negative side effects of chemotherapy and radiotherapy. Previously, we showed that the extracellular carbohydrate polymer of a Synechocystis ΔsigF overproducing mutant displayed a strong antitumor activity towards several human tumor cell lines, by inducing high levels of apoptosis through p53 and caspase-3 activation. Here, the ΔsigF polymer was manipulated to obtain variants that were tested in a human melanoma (Mewo) cell line. Our results demonstrated that high molecular mass fractions were important for the polymer bioactivity, and that the reduction of the peptide content generated a variant with enhanced in vitro antitumor activity. This variant, and the original ΔsigF polymer, were further tested in vivo using the chick chorioallantoic membrane (CAM) assay. Both polymers significantly decreased xenografted CAM tumor growth and affected tumor morphology, by promoting less compact tumors, validating their antitumor potential in vivo. This work contributes with strategies for the design and testing tailored cyanobacterial extracellular polymers and further strengths the relevance of evaluating this type of polymers for biotechnological/biomedical applications.info:eu-repo/semantics/publishedVersio

Automatic planning of the lower extremities for total marrow irradiation using volumetric modulated arc therapy

Purpose Total marrow (and lymphoid) irradiation (TMI-TMLI) is limited by the couch travel range of modern linacs, which forces the treatment delivery to be split into two plans with opposite orientations: a head-first supine upper-body plan, and a feet-first supine lower extremities plan. A specific field junction is thus needed to obtain adequate target coverage in the overlap region of the two plans. In this study, an automatic procedure was developed for field junction creation and lower extremities plan optimization. Methods Ten patients treated with TMI-TMLI at our institution were selected retrospectively. The planning of the lower extremities was performed automatically. Target volume parameters (CTV_J-V-98% > 98%) at the junction region and several dose statistics (D-98%, D-mean, and D-2%) were compared between automatic and manual plans. The modulation complexity score (MCS) was used to assess plan complexity. Results The automatic procedure required 60-90 min, depending on the case. All automatic plans achieved clinically acceptable dosimetric results (CTV_J-V-98% > 98%), with significant differences found at the junction region, where D-mean and D-2% increased on average by 2.4% (p < 0.03) and 3.0% (p < 0.02), respectively. Similar plan complexity was observed (median MCS = 0.12). Since March 2022, the automatic procedure has been introduced in our clinic, reducing the TMI-TMLI simulation-to-delivery schedule by 2 days. Conclusion The developed procedure allowed treatment planning of TMI-TMLI to be streamlined, increasing efficiency and standardization, preventing human errors, while maintaining the dosimetric plan quality and complexity of manual plans. Automated strategies can simplify the future adoption and clinical implementation of TMI-TMLI treatments in new centers

Internal Guidelines for Reducing Lymph Node Contour Variability in Total Marrow and Lymph Node Irradiation

Background: The total marrow and lymph node irradiation (TMLI) target includes the bones, spleen, and lymph node chains, with the latter being the most challenging structures to contour. We evaluated the impact of introducing internal contour guidelines to reduce the inter- and intraobserver lymph node delineation variability in TMLI treatments. Methods: A total of 10 patients were randomly selected from our database of 104 TMLI patients so as to evaluate the guidelines' efficacy. The lymph node clinical target volume (CTV_LN) was recontoured according to the guidelines (CTV_LN_GL_RO1) and compared to the historical guidelines (CTV_LN_Old). Both topological (i.e., Dice similarity coefficient (DSC)) and dosimetric (i.e., V95 (the volume receiving 95% of the prescription dose) metrics were calculated for all paired contours. Results: The mean DSCs were 0.82 ± 0.09, 0.97 ± 0.01, and 0.98 ± 0.02, respectively, for CTV_LN_Old vs. CTV_LN_GL_RO1, and between the inter- and intraobserver contours following the guidelines. Correspondingly, the mean CTV_LN-V95 dose differences were 4.8 ± 4.7%, 0.03 ± 0.5%, and 0.1 ± 0.1%. Conclusions: The guidelines reduced the CTV_LN contour variability. The high target coverage agreement revealed that historical CTV-to-planning-target-volume margins were safe, even if a relatively low DSC was observed

Impact of the Extremities Positioning on the Set-Up Reproducibility for the Total Marrow Irradiation Treatment

Total marrow (lymph node) irradiation (TMI/TMLI) delivery requires more time than standard radiotherapy treatments. The patient's extremities, through the joints, can experience large movements. The reproducibility of TMI/TMLI patients' extremities was evaluated to find the best positioning and reduce unwanted movements. Eighty TMI/TMLI patients were selected (2013-2022). During treatment, a cone-beam computed tomography (CBCT) was performed for each isocenter to reposition the patient. CBCT-CT pairs were evaluated considering: (i) online vector shift (OVS) that matched the two series; (ii) residual vector shift (RVS) to reposition the patient's extremities; (iii) qualitative agreement (range 1-5). Patients were subdivided into (i) arms either leaning on the frame or above the body; (ii) with or without a personal cushion for foot positioning. The Mann-Whitney test was considered (p < 0.05 significant). Six-hundred-twenty-nine CBCTs were analyzed. The median OVS was 4.0 mm, with only 1.6% of cases ranked < 3, and 24% of RVS > 10 mm. Arms leaning on the frame had significantly smaller RVS than above the body (median: 8.0 mm/6.0 mm, p < 0.05). Using a personal cushion for the feet significantly improved the RVS than without cushions (median: 8.5 mm/1.8 mm, p < 0.01). The role and experience of the radiotherapy team are fundamental to optimizing the TMI/TMLI patient setup