Symmetry Breaking in C. elegans: Another Gift from the Sperm

Polarization of the C. elegans embryo depends on the sperm-contributed centrosome, which cues a retraction of the actomyosin cortex to the opposite end of the embryo by an unknown mechanism. New evidence reveals that the sperm donates a second polarizing cue that may locally relax the actomyosin cortex near the point of sperm entry

CRISPR-Based Methods for Caenorhabditis elegans Genome Engineering

The advent of genome editing techniques based on the clustered regularly interspersed short palindromic repeats (CRISPR)–Cas9 system has revolutionized research in the biological sciences. CRISPR is quickly becoming an indispensible experimental tool for researchers using genetic model organisms, including the nematode Caenorhabditis elegans. Here, we provide an overview of CRISPR-based strategies for genome editing in C. elegans. We focus on practical considerations for successful genome editing, including a discussion of which strategies are best suited to producing different kinds of targeted genome modifications

China Maritime Report No. 5: China\u27s Dreadnought? The PLA Navy\u27s Type 055 Cruiser and Its Implications for the Future Maritime Security Environment

China’s naval modernization, a process that has been underway in earnest for three decades, is now hitting its stride. The advent of the Type 055 cruiser firmly places the PLAN among the world’s very top naval services. This study, which draws upon a unique set of Chinese-language writings, offers the first comprehensive look at this new, large surface combatant. It reveals a ship that has a stealthy design, along with a potent and seemingly well-integrated sensor suite. With 112 VLS cells, moreover, China’s new cruiser represents a large magazine capacity increase over legacy surface combatants. Its lethality might also be augmented as new, cutting edge weaponry could later be added to the accommodating design. This vessel, therefore, provides very substantial naval capability to escort Chinese carrier groups, protect Beijing’s long sea lanes, and take Chinese naval diplomacy to an entirely new and daunting level. Even more significant perhaps, the Type 055 will markedly expand the range and firepower of the PLAN and this could substantially impact myriad potential conflict scenarios, from the Indian Ocean to the Korean Peninsula and many in between. This study of Type 055 development, moreover, does yield evidence that Chinese naval strategists are acutely aware of major dilemmas confronting the U.S. Navy surface fleet.https://digital-commons.usnwc.edu/cmsi-maritime-reports/1004/thumbnail.jp

From Lyapunov modes to the exponents for hard disk systems

We demonstrate the preservation of the Lyapunov modes by the underlying tangent space dynamics of hard disks. This result is exact for the zero modes and correct to order $\epsilon$ for the transverse and LP modes where $\epsilon$ is linear in the mode number. For sufficiently large mode numbers the dynamics no longer preserves the mode structure. We propose a Gram-Schmidt procedure based on orthogonality with respect to the centre space that determines the values of the Lyapunov exponents for the modes. This assumes a detailed knowledge of the modes, but from that predicts the values of the exponents from the modes. Thus the modes and the exponents contain the same information

Single-object Imaging and Spectroscopy to Enhance Dark Energy Science from LSST

Single-object imaging and spectroscopy on telescopes with apertures ranging from ~4 m to 40 m have the potential to greatly enhance the cosmological constraints that can be obtained from LSST. Two major cosmological probes will benefit greatly from LSST follow-up: accurate spectrophotometry for nearby and distant Type Ia supernovae will expand the cosmological distance lever arm by unlocking the constraining power of high-z supernovae; and cosmology with time delays of strongly-lensed supernovae and quasars will require additional high-cadence imaging to supplement LSST, adaptive optics imaging or spectroscopy for accurate lens and source positions, and IFU or slit spectroscopy to measure detailed properties of lens systems. We highlight the scientific impact of these two science drivers, and discuss how additional resources will benefit them. For both science cases, LSST will deliver a large sample of objects over both the wide and deep fields in the LSST survey, but additional data to characterize both individual systems and overall systematics will be key to ensuring robust cosmological inference to high redshifts. Community access to large amounts of natural-seeing imaging on ~2-4 m telescopes, adaptive optics imaging and spectroscopy on 8-40 m telescopes, and high-throughput single-target spectroscopy on 4-40 m telescopes will be necessary for LSST time domain cosmology to reach its full potential. In two companion white papers we present the additional gains for LSST cosmology that will come from deep and from wide-field multi-object spectroscopy.Comment: Submitted to the call for Astro2020 science white paper

Salvage of failed free flaps used in head and neck reconstruction

Free flap success rates are in excess of 95%. Vascular occlusion (thrombosis) remains the primary reason for flap loss, with venous thrombosis being more common than arterial occlusion. The majority of flap failures occur within the first 48 hours. With early recognition and intervention of flap compromise salvage is possible. Successful salvage rates range from 28% to over 90%. Rapid re-exploration in this clinical setting is crucial to maximise the chances of flap salvage. If salvage is not feasible or unsuccessful then non-surgical methods of salvage may be employed with some possibility of success. The purpose of this article is to review the causes of free flap failure and to highlight the available options for salvage