Verifying continuous-variable entanglement in finite spaces

Starting from arbitrary Hilbert spaces, we reduce the problem to verify entanglement of any bipartite quantum state to finite dimensional subspaces. Hence, entanglement is a finite dimensional property. A generalization for multipartite quantum states is also given.Comment: 4 page

Rabl's model of the interphase chromosome arrangement tested in Chinise hamster cells by premature chromosome condensation and laser-UV-microbeam experiments

In 1885 Carl Rabl published his theory on the internal structure of the interphase nucleus. We have tested two predictions of this theory in fibroblasts grown in vitro from a female Chinese hamster, namely (1) the Rabl-orientation of interphase chromosomes and (2) the stability of the chromosome arrangement established in telophase throughout the subsequent interphase. Tests were carried out by premature chromosome condensation (PCC) and laser-UV-microirradiation of the interphase nucleus. Rabl-orientation of chromosomes was observed in G1 PCCs and G2 PCCs. The cell nucleus was microirradiated in G1 at one or two sites and pulse-labelled with 3H-thymidine for 2h. Cells were processed for autoradiography either immediately thereafter or after an additional growth period of 10 to 60h. Autoradiographs show unscheduled DNA synthesis (UDS) in the microirradiated nuclear part(s). The distribution of labelled chromatin was evaluated in autoradiographs from 1035 cells after microirradiation of a single nuclear site and from 253 cells after microirradiation of two sites. After 30 to 60h postincubation the labelled regions still appeared coherent although the average size of the labelled nuclear area fr increased from 14.2% (0h) to 26.5% (60h). The relative distance dr, i.e. the distance between two microirradiated sites divided by the diameter of the whole nucleus, showed a slight decrease with increasing incubation time. Nine metaphase figures were evaluated for UDS-label after microirradiation of the nuclear edge in G1. An average of 4.3 chromosomes per cell were labelled. Several chromosomes showed joint labelling of both distal chromosome arms including the telomeres, while the centromeric region was free from label. This label pattern is interpreted as the result of a V-shaped orientation of these particular chromosomes in the interphase nucleus with their telomeric regions close to each other at the nuclear edge. Our data support the tested predictions of the Rabl-model. Small time-dependent changes of the nuclear space occupied by single chromosomes and of their relative positions in the interphase nucleus seem possible, while the territorial organization of interphase chromosomes and their arrangement in general is maintained during interphase. The present limitations of the methods used for this study are discussed

Strongly entangled light from planar microcavities

The emission of entangled light from planar semiconductor microcavities is studied and the entanglement properties are analyzed and quantified. Phase-matching of the intra-cavity scattering dynamics for multiple pump beams or pulses, together with the coupling to external radiation, leads to the emission of a manifold of entangled photon pairs. A decomposition of the emitted photons into two parties leads to a strong entanglement of the resulting bipartite system. For the quantification of the entanglement, the Schmidt number of the system is determined by the construction of Schmidt number witnesses. It is analyzed to which extend the resources of the originally strongly entangled light field are diminished by dephasing in propagation channels.Comment: 9 pages, 5 figures, extended versio

Seed systems smallholder farmers use

Seed can be an important entry point for promoting productivity, nutrition and resilience among smallholder farmers. While investments have primarily focused on strengthening the formal sector, this article documents the degree to which the informal sector remains the core for seed acquisition, especially in Africa. Conclusions drawn from a uniquely comprehensive data set, 9660 observations across six countries and covering 40 crops, show that farmers access 90.2 % of their seed from informal systems with 50.9 % of that deriving from local markets. Further, 55 % of seed is paid for by cash, indicating that smallholders are already making important investments in this arena. Targeted interventions are proposed for rendering formal and informal seed sector more smallholder-responsive and for scaling up positive impacts

Limitations for change detection in multiple Gabor targets

We investigate the limitations on the ability to detect when a target has changed, using Gabor targets as simple quantifiable stimuli. Using a partial report technique to equalise response variables, we show that the log of the Weber fraction for detecting a spatial frequency change is proportional to the log of the number of targets, with a set-size effect that is greater than that reported for visual search. This is not a simple perceptual limitation, because pre-cueing a single target out of four restores performance to the level found when only one target is present. It is argued that the primary limitation on performance is the division of attention across multiple targets, rather than decay within visual memory. However in a simplified change detection experiment without cueing, where only one target of the set changed, not only was the set size effect still larger, but it was greater at 2000 msec ISI than at 250 msec ISI, indicating a possible memory component. The steepness of the set size effects obtained suggests that even moderate complexity of a stimulus in terms of number of component objects can overload attentional processes, suggesting a possible low-level mechanism for change blindness

Nijmegen Breakage Syndrome fibroblasts and iPSCs: cellular models for uncovering disease-associated signaling pathways and establishing a screening platform for anti-oxidants.

Nijmegen Breakage Syndrome (NBS) is associated with cancer predisposition, premature aging, immune deficiency, microcephaly and is caused by mutations in the gene coding for NIBRIN (NBN) which is involved in DNA damage repair. Dermal-derived fibroblasts from NBS patients were reprogrammed into induced pluripotent stem cells (iPSCs) in order to bypass premature senescence. The influence of antioxidants on intracellular levels of ROS and DNA damage were screened and it was found that EDHB-an activator of the hypoxia pathway, decreased DNA damage in the presence of high oxidative stress. Furthermore, NBS fibroblasts but not NBS-iPSCs were found to be more susceptible to the induction of DNA damage than their healthy counterparts. Global transcriptome analysis comparing NBS to healthy fibroblasts and NBS-iPSCs to embryonic stem cells revealed regulation of P53 in NBS fibroblasts and NBS-iPSCs. Cell cycle related genes were down-regulated in NBS fibroblasts. Furthermore, oxidative phosphorylation was down-regulated and glycolysis up-regulated specifically in NBS-iPSCs compared to embryonic stem cells. Our study demonstrates the utility of NBS-iPSCs as a screening platform for anti-oxidants capable of suppressing DNA damage and a cellular model for studying NBN de-regulation in cancer and microcephaly