517352 research outputs found
Sort by
Light- and Temperature-Controlled Hybridization, Chiral Induction and Handedness of Helical Foldamers
No full textHelical foldamers have attracted much attention over the last decades given their resemblance to certain biomacromolecules and their potential in domains as different as pharmaceutics, catalysis and photonics. Various research groups have successfully controlled the right- or left- handedness of these oligomers by introducing stereogenic centers through covalent or non-covalent chemistry. However, developing helical structures whose handedness can be reversibly switched remains a major challenge for chemists. To date, such an achievement has been reported with light-responsive single-stranded foldamers only. Herein, we demonstrate that grafting a unidirectional motor onto foldamer strands constitutes a relevant strategy to i) control the single or double helical state of a foldamer, ii) switch on the chiral induction process from the motor to the helical strands and iii) select the handedness of double helical structures through photochemical and thermal stimulations.</p
A Multiresponsive Ferrocene-Based Chiral Overcrowded Alkene Twisting Liquid Crystals
No full textThe reversible modulation of chirality has gained significant attention not only for fundamental stereochemical studies but also for numerous applications ranging from liquid crystals (LCs) to molecular motors and machines. This requires the construction of switchable molecules with (multiple) chiral elements in a highly enantioselective manner, which is often a significant synthetic challenge. Here, we show that the dimerization of an easily accessible enantiopure planar chiral ferrocene-indanone building block affords a multi-stimuli-responsive dimer (FcD) with pre-determined double bond geometry, helical chirality, and relative orientation of the two ferrocene motifs in high yield. This intrinsically planar chiral switch can not only undergo thermal or photochemical E/Z isomerization but can also be reversibly and quantitatively oxidized to both a monocationic and a dicationic state which is associated with significant changes in its (chir)optical properties. Specifically, FcD acts as a chiral dopant for cholesteric LCs with a helical twisting power (HTP) of 13 µm-1 which, upon oxidation, drops to near zero, resulting in an unprecedently large redox-tuning of the LC reflection color by up to 84 nm. Due to the straightforward stereoselective synthesis, FcD, and related chiral switches, are envisioned to be powerful building blocks for multi-stimuli-responsive molecular machines and in LC-based materials.</p
The Least Information Set Needed by Privacy Attackers
No full textThis paper studies privacy-preserving problems focusing on the information that is available to the attacker. For a class of general linear average consensus algorithms, we identify the least information set required by an attacker to infer the initial value of the target node. We then propose a novel algorithm that protects the initial value effectively if the attacker fails to have this least information. Furthermore, we show that the initial value of nodes may be disclosed even if the attacker does not know any information exchanged between the target node and its neighbors. Finally, we propose a novel eavesdropping algorithm if the least information is available. Several numerical examples are given to verify the validity of our results.</p
Light- and Temperature-Controlled Hybridization, Chiral Induction and Handedness of Helical Foldamers
No full textHelical foldamers have attracted much attention over the last decades given their resemblance to certain biomacromolecules and their potential in domains as different as pharmaceutics, catalysis and photonics. Various research groups have successfully controlled the right- or left- handedness of these oligomers by introducing stereogenic centers through covalent or non-covalent chemistry. However, developing helical structures whose handedness can be reversibly switched remains a major challenge for chemists. To date, such an achievement has been reported with light-responsive single-stranded foldamers only. Herein, we demonstrate that grafting a unidirectional motor onto foldamer strands constitutes a relevant strategy to i) control the single or double helical state of a foldamer, ii) switch on the chiral induction process from the motor to the helical strands and iii) select the handedness of double helical structures through photochemical and thermal stimulations.</p
The Least Information Set Needed by Privacy Attackers
No full textThis paper studies privacy-preserving problems focusing on the information that is available to the attacker. For a class of general linear average consensus algorithms, we identify the least information set required by an attacker to infer the initial value of the target node. We then propose a novel algorithm that protects the initial value effectively if the attacker fails to have this least information. Furthermore, we show that the initial value of nodes may be disclosed even if the attacker does not know any information exchanged between the target node and its neighbors. Finally, we propose a novel eavesdropping algorithm if the least information is available. Several numerical examples are given to verify the validity of our results.</p
A Multiresponsive Ferrocene-Based Chiral Overcrowded Alkene Twisting Liquid Crystals
No full textThe reversible modulation of chirality has gained significant attention not only for fundamental stereochemical studies but also for numerous applications ranging from liquid crystals (LCs) to molecular motors and machines. This requires the construction of switchable molecules with (multiple) chiral elements in a highly enantioselective manner, which is often a significant synthetic challenge. Here, we show that the dimerization of an easily accessible enantiopure planar chiral ferrocene-indanone building block affords a multi-stimuli-responsive dimer (FcD) with pre-determined double bond geometry, helical chirality, and relative orientation of the two ferrocene motifs in high yield. This intrinsically planar chiral switch can not only undergo thermal or photochemical E/Z isomerization but can also be reversibly and quantitatively oxidized to both a monocationic and a dicationic state which is associated with significant changes in its (chir)optical properties. Specifically, FcD acts as a chiral dopant for cholesteric LCs with a helical twisting power (HTP) of 13 µm-1 which, upon oxidation, drops to near zero, resulting in an unprecedently large redox-tuning of the LC reflection color by up to 84 nm. Due to the straightforward stereoselective synthesis, FcD, and related chiral switches, are envisioned to be powerful building blocks for multi-stimuli-responsive molecular machines and in LC-based materials.</p
Childhood Maltreatment and Revictimization:A Systematic Literature Review
No full textThere is established evidence that childhood/adolescent victimization is associated with victimization in adulthood although the underlying mechanisms are not still clear. The current study aimed to systematically review empirical studies examining potential psychological factors linking childhood maltreatment to victimization in adulthood and the gaps in the literature. Following PRISMA protocol, 71 original studies consisting of a total sample of n = 31,633 subjects were analyzed. Symptom severity for various trauma-related disorders, dissociation, emotion dysregulation, and risky sexual behaviors emerged as potential predictors of revictimization. While these potential risk factors mediate the relationship between childhood maltreatment and adulthood victimization, evidence for additional factors such as social support, attachment styles, maladaptive schemas, and risk detection is very limited. Addressing these intrapersonal risk factors, found by prior studies, in interventions and preventive programs might decrease the probability of revictimization. The interactions between the identified risk factors have not been studied well yet. Hence, more research on mediating risk factors of revictimization is needed. </p
Willingness to participate in combination screening for lung cancer, chronic obstructive pulmonary disease and cardiovascular disease in four European countries
No full textObjectives: Lung cancer screening (LCS), using low-dose computed tomography (LDCT), can be more efficient by simultaneously screening for chronic obstructive pulmonary disease (COPD) and cardiovascular disease (CVD), the Big-3 diseases. This study aimed to determine the willingness to participate in (combinations of) Big-3 screening in four European countries and the relative importance of amendable participation barriers. Methods: An online cross-sectional survey aimed at (former) smokers aged 50–75 years elicited the willingness of individuals to participate in Big-3 screening and used analytical hierarchy processing (AHP) to determine the importance of participation barriers. Results: Respondents were from France (n = 391), Germany (n = 338), Italy (n = 399), and the Netherlands (n = 342), and consisted of 51.2% men. The willingness to participate in screening was marginally influenced by the diseases screened for (maximum difference of 3.1%, for Big-3 screening (73.4%) vs. lung cancer and COPD screening (70.3%)) and by country (maximum difference of 3.7%, between France (68.5%) and the Netherlands (72.3%)). The largest effect on willingness to participate was personal perceived risk of lung cancer. The most important barriers were the missed cases during screening (weight 0.19) and frequency of screening (weight 0.14), while diseases screened for (weight 0.11) ranked low. Conclusions: The difference in willingness to participate in LCS showed marginal increase with inclusion of more diseases and limited variation between countries. A marginal increase in participation might result in a marginal additional benefit of Big-3 screening. The amendable participation barriers are similar to previous studies, and the new criterion, diseases screened for, is relatively unimportant. Clinical relevance statement: Adding diseases to combination screening modestly improves participation, driven by personal perceived risk. These findings guide program design and campaigns for lung cancer and Big-3 screening. Benefits of Big-3 screening lie in long-term health and economic impact, not participation increase. Key Points: • It is unknown whether or how combination screening might affect participation. • The addition of chronic obstructive pulmonary disease and cardiovascular disease to lung cancer screening resulted in a marginal increase in willingness to participate. • The primary determinant influencing individuals' engagement in such programs is their personal perceived risk of the disease.</p
Hours worked and the U.S. distribution of real annual earnings 1976-2019
No full textWe examine the impact of annual hours worked on annual earnings bydecomposing changes in the real annual earnings distribution intocomposition, structural and hours effects. We do so via a nonseparablesimultaneous model of hours, wages and earnings. Using the CurrentPopulation Survey for the survey years 1976--2019, we find that changes inthe female distribution of annual hours of work are important in explainingmovements in inequality in female annual earnings. This captures thesubstantial changes in their employment behavior over this period. Movementsin the male hours distribution only affect the lower part of their earningsdistribution and reflect the sensitivity of these workers' annual hours ofwork to cyclical factors
