Exploiting lens aberrations to create electron vortex beams

A model for a new electron vortex beam production method is proposed and experimentally demonstrated. The technique calls on the controlled manipulation of the degrees of freedom of the lens aberrations to achieve a helical phase front. These degrees of freedom are accessible by using the corrector lenses of a transmission electron microscope. The vortex beam is produced through a particular alignment of these lenses into a specifically designed astigmatic state and applying an annular aperture in the condensor plane. Experimental results are found to be in good agreement with simulations.Comment: 5 pages, 4 figure

Theory and applications of free-electron vortex states

Both classical and quantum waves can form vortices: with helical phase fronts and azimuthal current densities. These features determine the intrinsic orbital angular momentum carried by localized vortex states. In the past 25 years, optical vortex beams have become an inherent part of modern optics, with many remarkable achievements and applications. In the past decade, it has been realized and demonstrated that such vortex beams or wavepackets can also appear in free electron waves, in particular, in electron microscopy. Interest in free-electron vortex states quickly spread over different areas of physics: from basic aspects of quantum mechanics, via applications for fine probing of matter (including individual atoms), to high-energy particle collision and radiation processes. Here we provide a comprehensive review of theoretical and experimental studies in this emerging field of research. We describe the main properties of electron vortex states, experimental achievements and possible applications within transmission electron microscopy, as well as the possible role of vortex electrons in relativistic and high-energy processes. We aim to provide a balanced description including a pedagogical introduction, solid theoretical basis, and a wide range of practical details. Special attention is paid to translate theoretical insights into suggestions for future experiments, in electron microscopy and beyond, in any situation where free electrons occur.Comment: 87 pages, 34 figure

Fate specification and tissue-specific cell cycle control of the <i>Caenorhabditis elegans</i> intestine

Coordination between cell fate specification and cell cycle control in multicellular organisms is essential to regulate cell numbers in tissues and organs during development, and its failure may lead to oncogenesis. In mammalian cells, as part of a general cell cycle checkpoint mechanism, the F-box protein β-transducin repeat-containing protein (β-TrCP) and the Skp1/Cul1/F-box complex control the periodic cell cycle fluctuations in abundance of the CDC25A and B phosphatases. Here, we find that the Caenorhabditis elegans β-TrCP orthologue LIN-23 regulates a progressive decline of CDC-25.1 abundance over several embryonic cell cycles and specifies cell number of one tissue, the embryonic intestine. The negative regulation of CDC-25.1 abundance by LIN-23 may be developmentally controlled because CDC-25.1 accumulates over time within the developing germline, where LIN-23 is also present. Concurrent with the destabilization of CDC-25.1, LIN-23 displays a spatially dynamic behavior in the embryo, periodically entering a nuclear compartment where CDC-25.1 is abundant

Developmental control of cell division

During development of multicellular organisms, cell divisions need to be coordinated with the developmental program of the entire organism. Although the mechanisms that drive cells through the division cycle are well understood, very little is known about the pathways that link extracellular signals to the cell-intrinsic cell-cycle machinery. We used the nematode Caenorhabditis elegans as a model system to study the control of cell-cycle progression during development of a multicellular organism. C. elegans provides a unique animal model in which developmental controls of cell-division can be identified genetically. Cell divisions can be followed in vivo by light microscopy, and the nearly invariant cell-lineage of C. elegans has been completely described. In addition, redundancy between genes is limited in C. elegans. Finally, powerful genetic techniques are available in C. elegans to study gene function. To use C. elegans as a model system to identify developmental regulators of cell-cycle progression, we first needed to identify the basic cell-cycle machinery in C. elegans. We demonstrated that ncc-1 CDK1 is required specifically for entry into mitosis and progression through meiosis. In addition, an ortholog of CDK4/CDK6 kinases (cdk-4), and a D-type cyclin (cyd-1) are required for G1 progression of postembryonic somatic cells. Furthermore, a homolog of the mammalian Cip/Kip kinase inhibitors, cki-1, was shown to negatively regulate cell-cycle progression. Finally, we determined the role of lin-35 Rb, efl-1 E2F and dpl-1 DP in G1 progression and found that lin-35 and efl-1 are negative regulators of G1 progression while dpl-1 has aspects of both a positive regulator and a negative regulator. In each case, the C. elegans cell-cycle gene acts in a similar fashion as its mammalian counterpart. These results established C. elegans as an attractive genetic system in which to study cell-cycle regulation, as results obtained in C. elegans will likely be applicable to cell-cycle regulation in mammals. The major strength of studies in C. elegans is the ability to use genetic techniques to identify novel genes. We performed several screens to identify novel regulators of G1 progression. The cell-cycle regulators lin-35 Rb, efl-1 E2F and dpl-1 Dp are also members of the synthetic Multivulva (synMuv) gene family, which regulates vulval cell fate specification. Using a reverse genetic approach, we identified a role for three additional synMuv genes (lin-9 Aly, lin-15B and lin-36) as negative regulators of G1 progression. These genes all encode proteins for which no function in G1 regulation had previously been described. In addition to this reverse getic approach, we performed classical genetic screens to identify novel targets of cyd-1 and genes that cooperate with lin-35 Rb during development of C. elegans. One of the identified mutations likely defines a gene that acts downstream of cyd-1. In addition, we have already identified mutations whose phenotype is rescued by loss of lin-35, and mutations that are lethal only when combined with inactivation of lin-35. These preliminary results show that these screens have great potential to identify novel cell-cycle regulators

Sustainable School Buildings: Some of the Latest Dutch Examples of Nearly zero Emissions Buildings

In the Netherlands with respect to sustainable educational building there is a continuous development going on from sustainable building, to Passive House schools, to nearly Zero Emission Buildings to even Energy positive buildings. The Dutch government started a special funding program to stimulate the innovation of high performance schools. Some of these schools were built as extreme sustainability friendly schools while also much attention was given to comfort and health aspects. Three of these new schools were investigated: two passive house schools and the first net ZEB designed school are analyzed, measured and their results were compared with 13 other recent but more traditional designed schools, as well as with schools from earlier research. The results showed that concerning Indoor Air Quality and thermal comfort the new environmental schools did not perform very well. This is a disappointing result which indicates that is necessary to pay enough attention to the basic functionalities of a school (health and comfortable indoor environment) instead of focusing too much on sustainability

Associations of periconception dietary glycemic index and load with fertility in women and men:a study among couples in the general population

Background: The dietary glycemic index (GI) and load (GL) reflect carbohydrate quality and quantity, potentially impacting fertility through modulation of insulin sensitivity and generation of oxidative stress. While fertility is influenced by both women and men, reproductive research often emphasizes maternal factors. We first examined periconception dietary intake in both women and male partners, and subsequent associations of dietary GI and GL with fecundability and subfertility. Methods: Among 830 women and 651 male partners, participating in a population-based prospective cohort study from preconception onwards, we assessed periconception dietary intake and calculated GI and GL, using a food frequency questionnaire (FFQ) at median 12.4 weeks gestation (95% range 10.9, 18.4). Information on time to pregnancy was obtained through questionnaires, with subfertility defined as a time to pregnancy ≥ 12 months or use of assisted reproductive technology. Results: In the periconception period, mean energy intake in women was 1870 kcal (SD: 500; 46% carbohydrates, 16% protein, 33% fat; dietary GI 56.2 (SD: 3.5) and GL 141.4 (SD: 67.4)). Mean energy intake in men was 2350 kcal (SD: 591; 43% carbohydrates, 16% protein, 33% fat; dietary GI 56.8 (SD: 3.2) and GL 156.7 (SD: 75.4)). Median time to pregnancy was 4.8 months (IQR: 1.2, 16.4), with 30.6% of 830 women experiencing subfertility. Dietary GI and GL were not associated with fertility outcomes in women. In men, higher dietary GI and GL across the full range were associated with decreased fecundability, after adjusting for socio-demographic and lifestyle factors, as well as dietary GI or GL of female partners [FR: 0.91, 95% CI 0.83, 0.99; FR: 0.90, 95% CI 0.81, 0.99, per SDS increase in dietary GI and GL, respectively]. When assessing the combined influence of dietary GI clinical categories in women and men, both partners adhering to a low GI diet tended to be associated with increased fecundability, but not with subfertility risk. Conclusions: Suboptimal periconception carbohydrate intake may be negatively associated with male fertility, but not with fertility outcomes in women. Further studies are needed to assess whether a lower GI and GL diet is a feasible lifestyle intervention to improve couples fertility.</p

Ontwikkeling bedrijfssysteem met luzerne op Cranendonck

Luzerne kan in droge jaren zonder kunstmatige beregening tot hoge opbrengsten komen en heeft geen stikstofbemesting nodig

Persoonlijke conditionering met regeltechnische 'human in the loop'-benadering

De behoefte aan individueel comfort heeft geleid tot de ontwikkeling van persoonlijke klimaatsystemen. Deze systemen hebben een positieve impact op het thermisch comfort en maken energiebesparing mogelijk doordat ze de energie meer lokaal en dus effectiever inzetten. De aansturing van deze systemen is nu nog traditioneel en niet optimaal. Een alternatief is wellicht om het menselijk lichaam als sensor te gebruiken en zo individuele klimaatsysteem aan te sturen

De mens als eigen sensor voor comfort

Dit artikel presenteert een nieuwe strategie voor de automatische regeling van individuele verwarming in licht koele kantooromgevingen, waarbij het menselijk lichaam als sensor wordt gebruikt in de klimaatregeling. De temperatuur van de bovenste extremiteiten, zoals vingers, handen, neus en voorhoofd, worden op afstand geregistreerd door infrarood (IR) thermografie en kunnen zo dienst doen als sensoren. Deze waarnemingen dienen als ingangssignaal voor de temperatuurregeling. Doel is het energiegebruik te verminderen met handhaving van het ondervonden thermisch comfort door de individuele gebouwgebruiker. Dit moet leiden tot nieuwe Smart Energy Systems, die met behulp van draadloze sensoren nieuwe, slimmere regelingen toepassen om de energievraag te reduceren. Tot 17% energiebesparing is mogelijk terwijl de gebruiker een optimaler individueel thermisch comfort ervaart