University of Hawaii at Manoa

About: University of Hawaii at Manoa is a education organization based out in Honolulu, Hawaii, United States. It is known for research contribution in the topics: Population & Sea surface temperature. The organization has 13693 authors who have published 25161 publications receiving 1023924 citations.

A ∼ 0.2-solar-mass protostar with a Keplerian disk in the very young L1527 IRS system

Abstract: In the earliest stage of star formation, protostars accrete mass from their surrounding envelopes through circumstellar disks; observations of the protostar L1527 IRS find a large, rotating proto-planetary disk from which the protostellar mass is measured to be 0.19 solar masses, with a protostar-to-envelope mass ratio of about 0.2. This paper reports the use of submillimetre interferometry to obtain the first detection of a large Keplerian disk around a protostar in the earliest phase of evolution, the class 0 phase. Hitherto the smallest observed protostar-to-envelope mass ratio was about 2.1. The newly discovered protostar, L1527 IRS, has a mass of approximately 0.2 solar masses and a protostar-to-envelope mass ratio of about 0.2. L1527 already has a proto-planetary disk of at least seven Jupiter masses, similar to presumed planet-forming disks, so it appears to have all the elements of a solar system in the making. In their earliest stages, protostars accrete mass from their surrounding envelopes through circumstellar disks. Until now, the smallest observed protostar-to-envelope mass ratio was about 2.1 (ref. 1). The protostar L1527 IRS is thought to be in the earliest stages of star formation2. Its envelope contains about one solar mass of material within a radius of about 0.05 parsecs (refs 3, 4), and earlier observations suggested the presence of an edge-on disk5. Here we report observations of dust continuum emission and 13CO (rotational quantum number J = 2 → 1) line emission from the disk around L1527 IRS, from which we determine a protostellar mass of 0.19 ± 0.04 solar masses and a protostar-to-envelope mass ratio of about 0.2. We conclude that most of the luminosity is generated through the accretion process, with an accretion rate of about 6.6 × 10−7 solar masses per year. If it has been accreting at that rate through much of its life, its age is approximately 300,000 years, although theory suggests larger accretion rates earlier6, so it may be younger. The presence of a rotationally supported disk is confirmed, and significantly more mass may be added to its planet-forming region as well as to the protostar itself in the future.

Internal Tides in Monterey Submarine Canyon

Abstract: The M2 internal tide in Monterey Submarine Canyon is simulated using a modified version of the Princeton Ocean Model. Most of the internal tide energy entering the canyon is generated to the south, on Sur Slope and at the head of Carmel Canyon. The internal tide is topographically steered around the large canyon meanders. Depth-integrated baroclinic energy fluxes are up canyon and largest near the canyon axis, up to 1.5 kW m−1 at the mouth of the upper canyon and increasing to over 4 kW m−1 around Monterey and San Gregorio Meanders. The up-canyon energy flux is bottom intensified, suggesting that topographic focusing occurs. Net along-canyon energy flux decreases almost monotonically from 9 MW at the canyon mouth to 1 MW at Gooseneck Meander, implying that high levels of internal tide dissipation occur. The depth-integrated energy flux across the 200-m isobath is order 10 W m−1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head, where internal ti...

Function of sperm chromatin structural elements in fertilization and development

Abstract: Understanding how DNA is packaged in the mammalian sperm cell has important implications for human infertility as well as for the cell biology. Recent advances in the study of mammalian sperm chromatin structure and function have altered our perception of this highly condensed, inert chromatin. Sperm DNA is packaged very tightly to protect the DNA during the transit that occurs before fertilization. However, this condensation cannot sacrifice chromosomal elements that are essential for the embryo to access the correct sequences of the paternal genome for proper initiation of the embryonic developmental program. The primary levels of the sperm chromatin structure can be divided into three main categories: the large majority of DNA is packaged by protamines, a smaller amount (2-15%) retains histone-bound chromatin and the DNA is attached to the nuclear matrix at roughly 50 kb intervals. Current data suggest that the latter two structural elements are transferred to the paternal pronucleus after fertilization where they have important functional roles. The nuclear matrix organization is essential for DNA replication, and the histone-bound chromatin identifies genes that are important for embryonic development. These data support the emerging view of the sperm genome as providing, in addition to the paternal DNA sequence, a structural framework that includes molecular regulatory factors that are required for proper embryonic development.

Incremental Capacity Analysis and Close-to-Equilibrium OCV Measurements to Quantify Capacity Fade in Commercial Rechargeable Lithium Batteries

Abstract: A quantitative approach is used to identify sources of contribution of capacity fade in commercial rechargeable lithium battery cells in laboratory evaluations. Our approach comprises measurements of close-to-equilibrium open-circuit voltage (cte-OCV) of the cell after relaxation at the end of the charging and discharging regimes and an incremental capacity analysis, in addition to conventional cycle-life test protocols using the dynamic stress test schedule. This approach allows us to separate attributes to capacity fade due to intrinsic and extrinsic origins.

Seasonal Eddy Field Modulation of the North Pacific Subtropical Countercurrent: TOPEX/Poseidon Observations and Theory

Abstract: Altimetry data from the first 5…-yr TOPEX/Poseidon mission (October 1992‐December 1997) are analyzed focusing on the North Pacific Subtropical Countercurrent (STCC) near the center of the Pacific’s western subtropical gyre. The multiyear altimetry data reveal that the eastward-flowing STCC is a highly variable zonal current, whose area-averaged eddy kinetic energy level (338 cm 2 s22) reaches half the eddy kinetic energy level of the Kuroshio Extension. The eddy kinetic energy of the STCC has a well-defined annual cycle with a maximum in April/May and a minimum in December/January. The peak-to-peak amplitude of this seasonal eddy kinetic energy modulation exceeds 200 cm2 s22. No such distinct annual cycle of the eddy kinetic energy is found in any other zonal current of the North Pacific Ocean. Using a 2‰-layer reduced-gravity model representing the vertically sheared STCC‐North Equatorial Current (NEC) system, it is shown that the seasonal modulation of the STCC’s eddy field is a manifestation in the intensity of baroclinic instability. In spring the STCC‐NEC system has a large vertical velocity shear and a weak vertical stratification, subjecting it to strong baroclinic instability. In fall, reduction in the vertical velocity shear between the STCC and its underlying NEC, and intensification of the upper-layer stratification weakens the baroclinic instability. In comparison with the STCC of 198‐258N, the altimetry data reveal that the westward-flowing NEC existing between 10 8 and 158N has a relatively low eddy kinetic energy level, despite being a stronger vertically sheared zonal current than the STCC. That the NEC is less eddy energetic is shown to be due to both its presence in a low-latitude band and its unidirectional flow. Both of these factors make it more difficult to reverse the potential vorticity gradient of the mean state (i.e., satisfying the necessary condition for the baroclinic instability) in the NEC than in the STCC‐ NEC system.