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Tackling post-harvest cereal losses in sub-Saharan Africa
Post-harvest loss reduction raises food availability without increasing the use of land, water and agricultural inputs. This article refers to the case of grain to show the hurdles that farmers have to clear in taking measures to reduce losses and suggests ways that post-harvest practitioners can target mitigating actions in sub-Saharan Africa
Deep Synoptic Array Science: Polarimetry of 25 New Fast Radio Bursts Provides Insights into their Origins
We report on a full-polarization analysis of the first 25 as yet
non-repeating FRBs detected at 1.4 GHz by the 110-antenna Deep Synoptic Array
(DSA-110) during commissioning observations. We present details of the data
reduction, calibration, and analysis procedures developed for this novel
instrument. The data have 32 s time resolution and sensitivity to Faraday
rotation measures (RMs) between rad m. RMs are detected for
20 FRBs with magnitudes ranging from rad m. FRBs are
found to have high () linear-polarization fractions. The remaining
FRBs exhibit significant circular polarization (), or are either
partially depolarized () or unpolarized (). We investigate the
mechanism of depolarization, disfavoring stochastic RM variations within a
scattering screen as a dominant cause. Polarization-state and possible RM
variations are observed in the four FRBs with multiple sub-components, but only
one other FRB shows a change in polarization state. We combine the DSA-110
sample with polarimetry of previously published FRBs, and compare the
polarization properties of FRB sub-populations and FRBs with Galactic pulsars.
Although FRBs are typically far more polarized than the average profiles of
Galactic pulsars, and exhibit greater spread in polarization fractions than
pulsar single pulses, we find a remarkable similarity between FRB polarization
fractions and the youngest (characteristic ages yr) pulsars. Our
results support a scenario wherein FRB emission is intrinsically highly
linearly polarized, and where propagation effects within progenitor
magnetospheres can result in conversion to circular polarization and
depolarization. Young pulsar emission and magnetospheric-propagation geometries
may form a useful analogy for the origin of FRB polarization.Comment: 43 pages, 17 figure
Deep Synoptic Array Science: Implications of Faraday Rotation Measures of Localized Fast Radio Bursts
Faraday rotation measures (RMs) of fast radio bursts (FRBs) offer the
prospect of directly measuring extragalactic magnetic fields. We present an
analysis of the RMs of ten as yet non-repeating FRBs detected and localized to
host galaxies by the 110-antenna Deep Synoptic Array (DSA-110). We combine this
sample with published RMs of 15 localized FRBs, nine of which are repeating
sources. For each FRB in the combined sample, we estimate the host-galaxy
dispersion measure (DM) contributions and extragalactic RM. We find compelling
evidence that the extragalactic components of FRB RMs are often dominated by
contributions from the host-galaxy interstellar medium (ISM). Specifically, we
find that both repeating and as yet non-repeating FRBs show a correlation
between the host-DM and host-RM in the rest frame, and we find an
anti-correlation between extragalactic RM (in the observer frame) and redshift
for non-repeaters, as expected if the magnetized plasma is in the host galaxy.
Important exceptions to the ISM origin include a dense, magnetized circum-burst
medium in some repeating FRBs, and the intra-cluster medium (ICM) of host or
intervening galaxy clusters. We find that the estimated ISM magnetic-field
strengths, , are characteristically larger than those inferred from
Galactic radio pulsars. This suggests either increased ISM magnetization in FRB
hosts in comparison with the Milky Way, or that FRBs preferentially reside in
regions of increased magnetic-field strength within their hosts
A regulatory motif in nonmuscle myosin II-B regulates its role in migratory front-back polarity
In this study, we show that the role of nonmuscle myosin
II (NMII)-B in front–back migratory cell polarity is
controlled by a short stretch of amino acids containing
five serines (1935–1941). This motif resides near the
junction between the C terminus helical and nonhelical
tail domains. Removal of this motif inhibited NMII-B assembly,
whereas its insertion into NMII-A endowed an
NMII-B–like ability to generate large actomyosin bundles
that determine the rear of the cell. Phosphomimetic
mutation of the five serines also inhibited NMII-B assembly,
rendering it unable to support front–back polarization.
Mass spectrometric analysis showed that several of
these serines are phosphorylated in live cells. Single-site
mutagenesis showed that serine 1935 is a major regulatory
site of NMII-B function. These data reveal a novel regulatory
mechanism of NMII in polarized migrating cells
by identifying a key molecular determinant that confers
NMII isoform functional specificityThis work is supported by grants SAF2011-24953 from MINECO, FP7
Marie Curie CIG-293719 from the EU, CIVP16A1831 from the Ramon
Areces Foundation (M. Vicente-Manzanares), GM 23244 (A.R. Horwitz),
GM037537 (D.F. Hunt), and the Cell Migration Consortium U54 GM64346
(A.R. Horwitz and D.F. Hunt). M. Vicente-Manzanares is an investigator from
the Ramón y Cajal Program (RYC-2010-06094)
Deep Synoptic Array science I: discovery of the host galaxy of FRB 20220912A
We report the detection and interferometric localization of the repeating
fast radio burst (FRB) source FRB 20220912A during commissioning observations
with the Deep Synoptic Array (DSA-110). Two bursts were detected from FRB
20220912A, one each on 2022 October 18 and 2022 October 25. The best-fit
position is (R.A. J2000, decl. J2000) = (23:09:04.9, +48:42:25.4), with a 90%
confidence error ellipse of arcsec and arcsec in right ascension
and declination respectively. The two bursts have disparate polarization
properties and temporal profiles. We find a Faraday rotation measure that is
consistent with the low value of rad m reported by CHIME/FRB. The
DSA-110 localization overlaps with the galaxy PSO J347.2702+48.7066 at a
redshift , which we identify as the likely host. PSO
J347.270248.7066 has a stellar mass of approximately ,
modest internal dust extinction, and a star-formation rate likely in excess of
yr. The host-galaxy contribution to the dispersion
measure is likely pc cm. The FRB 20220912A source is
therefore likely viewed along a tenuous plasma column through the host galaxy.Comment: 10 pages, 7 figures, 2 tables, submitted to AAS Journal
RhoGTPase Regulators Orchestrate Distinct Stages of Synaptic Development
Small RhoGTPases regulate changes in post-synaptic spine morphology and density that support learning and memory. They are also major targets of synaptic disorders, including Autism. Here we sought to determine whether upstream RhoGTPase regulators, including GEFs, GAPs, and GDIs, sculpt specific stages of synaptic development. The majority of examined molecules uniquely regulate either early spine precursor formation or later matura- tion. Specifically, an activator of actin polymerization, the Rac1 GEF β-PIX, drives spine pre- cursor formation, whereas both FRABIN, a Cdc42 GEF, and OLIGOPHRENIN-1, a RhoA GAP, regulate spine precursor elongation. However, in later development, a novel Rac1 GAP, ARHGAP23, and RhoGDIs inactivate actomyosin dynamics to stabilize mature synap- ses. Our observations demonstrate that specific combinations of RhoGTPase regulatory pro- teins temporally balance RhoGTPase activity during post-synaptic spine development
Larger grain borer
The larger grain borer, Prostephanus truncatus is a species originating in Meso-America which was accidentally introduced to Tanzania and Togo. It has since spread widely, becoming the most destructive pest of stored maize in both East and West Africa.
Adult P. truncatus tunnel extensively in the grain, feeding directly on it and excavating side chambers, off the main tunnel, where the females lay a batch of 4 to 8 eggs. On hatching, the larvae tunnel into the grain within which the eggs are laid
Post-harvest management of sorghum
Sorghum is an important cereal, especially in the developing world where it is a major food source in regions where other cereal crops would not withstand the harsh conditions. After summarising sorghum’s nutritional status and world production figures, this chapter presents postharvest operations: harvesting, transport, threshing, drying, cleaning, packaging and storage, then dehulling and milling. Means of storage and their management, major pests and their control as well as toxins produced by fungi are discussed. The chapter then lists the major transformations of sorghum and their end products. Quality requirements are introduced to complete the chapter
Facing the food crisis: How African smallholders can reduce postharvest cereal losses by supplying better quality grain
In much of Sub-Saharan Africa (SSA) cereal grains such as maize, rice, sorghum and millet are the main food staples. While localised supply problems are a common occurrence, widespread food crises have been relatively rare. The food crisis initiated in 2006/2007 resulted in a change in development priorities, bringing an increased focus on agriculture and a renewed interest in the reduction of postharvest losses (PHLs) as a means of increasing food availability. In the case of smallholders, most cereals are stored by farming households after harvest until they are sold or consumed during the year, a key aspect of addressing postharvest losses is through encouraging smallholders to invest more of their resources in postharvest handling and storage to maintain the high quality of their cereals and reap the rewards of higher value markets. This article discusses the renewed interest in reducing postharvest cereal losses. It focuses particularly on recent developments in loss estimation and considers how grain quality improvement can contribute to loss reduction and the livelihoods of smallholder farmers in Sub-Saharan Africa
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