לוח שנה משולב

Hematopoietic stem cells (HSCs) and their subsequent progenitors produce blood cells, but the precise nature of this production is dogged by controversy. Cellular barcoding is a powerful experimental technique that simultaneously traces the in vivo differentiation of individual cells. Using cellular barcoding, we traced the progeny of hematopoietic progenitors and reconstituted the lineage relationship with single cell resolution. We show that individual multipotent progenitors are generally not multi-outcome; instead, they produce heterogeneous patterns of limited types of blood cells. Interestingly, we found that some progenitors produce dendritic cells without producing any lymphoid and myeloid cells, redefining dendritic cells as a third lineage of blood cells. We then developed a quantitative framework to infer the nature of the hematopoietic tree. With this approach, we showed that the classical model of hematopoiesis cannot explain our data and we propose an alternative model.

It is known that modeling uncertainties and astrophysical
foregrounds can potentially introduce appreciable bias in the deduced
values of cosmological parameters. While it is commonly assumed that these
uncertainties will be accounted for to a sufficient level of precision,
the level of bias has not been properly quantified in most cases of
interest. We show that the requirement that the bias in derived values of
cosmological parameters does not surpass nominal statistical error,
translates into a maximal level of overall error $O(N^{-1/2})$ on $|Delta
P(k)|/P(k)$ and $|Delta C_{l}|/C_{l}$, where $P(k)$, $C_{l}$, and $N$ are
the matter power spectrum, angular power spectrum, and number of
(independent Fourier) modes at a given scale $l$ or $k$ probed by the
cosmological survey, respectively. For example, future
redshifted-21-cm observations, projected to sample $sim 10^{14}$ modes,
will require knowledge of the matter power spectrum to a fantastic
$10^{-7}$ precision level; realizing the expected potential of future
cosmological surveys, which aim at detecting $10^{6}-10^{14}$ modes,
sets the formidable challenge of reducing the overall level of
uncertainty to $10^{-3}-10^{-7}$.