1,298 research outputs found
Analysis on the hull girder ultimate strength of a bulk carrier using simplified method based on an incremental-iterative approach
The hull girder ultimate strength of a typical bulk carrier is analyzed using a simplified method based on an incremental-iterative approach. First, vertical bending moment is examined by seven different methods. The moment versus curvature curves and the values of the ultimate longitudinal moments at collapse states are determined for both hogging and sagging cases. Second, the ultimate strength under coupled vertical and horizontal bending moment is accounted. An interaction curve is obtained, which corresponds to the results of series of calculation for the ship hull subject to bending conditions with different angles of curvature. It is found that the interaction curve is asymmetrical because the hull cross section is not symmetrical with respect to the horizontal axis and the structural response of the elements under compression is different from that under tension due to nonlinearity caused by buckling. The angles of the resultant bending moment vector and that of the curvature vector are different in investigated cases. The interaction design equations proposed by other researches are also addressed to discuss the results presented by this study
Spatial selectivity in human ventrolateral prefrontal cortex
The functional organization of lateral prefrontal cortex is not well understood, and there is debate as to whether the dorsal and ventral aspects mediate distinct spatial and non-spatial functions, respectively. We show for the first time that recordings from human ventrolateral prefrontal cortex show spatial selectivity, supporting the idea that ventrolateral prefrontal cortex is involved in spatial processing. Our results also indicate that prefrontal cortex may be a source of control signals for neuroprosthetic applications
Ataxia with oculomotor apraxia type 2: a clinical, pathologic, and genetic study
BACKGROUND: Ataxia with oculomotor apraxia type 2 (AOA2) is characterized by
onset between age 10 and 22 years, cerebellar atrophy, peripheral neuropathy,
oculomotor apraxia (OMA), and elevated serum alpha-fetoprotein (AFP) levels.
Recessive mutations in SETX have been described in AOA2 patients.
OBJECTIVE: To describe the clinical features of AOA2 and to identify the SETX
mutations in 10 patients from four Italian families.
METHODS: The patients underwent clinical examination, routine laboratory tests,
nerve conduction studies, sural nerve biopsy, and brain MRI. All were screened
for SETX mutations.
RESULTS: All the patients had cerebellar features, including limb and truncal
ataxia, and slurred speech. OMA was observed in two patients, extrapyramidal
symptoms in two, and mental impairment in three. High serum AFP levels, motor and
sensory axonal neuropathy, and marked cerebellar atrophy on MRI were detected in
all the patients who underwent these examinations. Sural nerve biopsy revealed a
severe depletion of large myelinated fibers in one patient, and both large and
small myelinated fibers in another. Postmortem findings are also reported in one
of the patients. Four different homozygous SETX mutations were found (a
large-scale deletion, a missense change, a single-base deletion, and a
splice-site mutation).
CONCLUSIONS: The clinical phenotype of oculomotor apraxia type 2 is fairly
homogeneous, showing only subtle intrafamilial variability. OMA is an inconstant
finding. The identification of new mutations expands the array of SETX variants,
and the finding of a missense change outside the helicase domain suggests the
existence of at least one more functional region in the N-terminus of senataxin
Remanence effects in the electrical resistivity of spin glasses
We have measured the low temperature electrical resistivity of Ag : Mn
mesoscopic spin glasses prepared by ion implantation with a concentration of
700 ppm. As expected, we observe a clear maximum in the resistivity (T ) at a
temperature in good agreement with theoretical predictions. Moreover, we
observe remanence effects at very weak magnetic fields for the resistivity
below the freezing temperature Tsg: upon Field Cooling (fc), we observe clear
deviations of (T ) as compared with the Zero Field Cooling (zfc); such
deviations appear even for very small magnetic fields, typically in the Gauss
range. This onset of remanence for very weak magnetic fields is reminiscent of
the typical signature on magnetic susceptibility measurements of the spin glass
transition for this generic glassy system
A New Frequency-Luminosity Relation for Long GRBs?
We have studied power density spectra (PDS) of 206 long Gamma-Ray Bursts
(GRBs). We fitted the PDS with a simple power-law and extracted the exponent of
the power-law (alpha) and the noise-crossing threshold frequency (f_th). We
find that the distribution of the extracted alpha peaks around -1.4 and that of
f_th around 1 Hz. In addition, based on a sub-set of 58 bursts with known
redshifts, we show that the redshift-corrected threshold frequency is
positively correlated with the isotropic peak luminosity. The correlation
coefficient is 0.57 +/- 0.03.Comment: 9 pages, 17 figures, 1 table; Accepted for publication in MNRA
Concomitant Tumor Immunity to a Poorly Immunogenic Melanoma Is Prevented by Regulatory T Cells
Concomitant tumor immunity describes immune responses in a host with a progressive tumor that rejects the same tumor at a remote site. In this work, concomitant tumor immunity was investigated in mice bearing poorly immunogenic B16 melanoma. Progression of B16 tumors did not spontaneously elicit concomitant immunity. However, depletion of CD4+ T cells in tumor-bearing mice resulted in CD8+ T cellâmediated rejection of challenge tumors given on day 6. Concomitant immunity was also elicited by treatment with cyclophosphamide or DTA-1 monoclonal antibody against the glucocorticoid-induced tumor necrosis factor receptor. Immunity elicited by B16 melanoma cross-reacted with a distinct syngeneic melanoma, but not with nonmelanoma tumors. Furthermore, CD8+ T cells from mice with concomitant immunity specifically responded to major histocompatibility complex class Iârestricted epitopes of two melanocyte differentiation antigens. RAG1â/â mice adoptively transferred with CD8+ and CD4+ T cells lacking the CD4+CD25+ compartment mounted robust concomitant immunity, which was suppressed by readdition of CD4+CD25+ cells. Naturally occurring CD4+CD25+ T cells efficiently suppressed concomitant immunity mediated by previously activated CD8+ T cells, demonstrating that precursor regulatory T cells in naive hosts give rise to effective suppressors. These results show that regulatory T cells are the major regulators of concomitant tumor immunity against this weakly immunogenic tumor
Intermediate Mass Black Hole Formation in compact Young Massive Star Clusters
Young dense massive star clusters are a promising environment for the
formation of intermediate mass black holes (IMBHs) through collisions. We
present a set of 80 simulations carried out with Nbody6++GPU of 10 initial
conditions for compact star clusters with
half-mass radii , central densities
, and resolved stellar
populations with 10\% primordial binaries. Very massive stars (VMSs) with
masses up to grow rapidly by binary exchange and three-body
scattering events with main sequences stars in hard binaries. Assuming that in
VMS - stellar BH collisions all stellar material is accreted onto the BH, IMBHs
with masses up to can form on timescales of
Myr. This process was qualitatively predicted from Monte Carlo
MOCCA simulations. Despite the stochastic nature of the process - typically not
more than 3/8 cluster realisations show IMBH formation - we find indications
for higher formation efficiencies in more compact clusters. Assuming a lower
accretion fraction of 0.5 for VMS - BH collisions, IMBHs can also form. The
process might not work for accretion fractions as low as 0.1. After formation,
the IMBHs can experience occasional mergers with stellar mass BHs in
intermediate mass-ratio inspiral events (IMRIs) on a 100 Myr timescale.
Realised with more than stars, 10 \% binaries, the assumed stellar
evolution model with all relevant evolution processes included and 300 Myr
simulation time, our large suite of simulations indicates that IMBHs of several
hundred solar masses might form rapidly in massive star clusters right after
their birth while they are still compact.Comment: Submitte
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