211 research outputs found
Electromagnetic Forces in a Hybrid Magnetic-Bearing Switched-Reluctance Motor
Analysis and experimental measurement of the electromagnetic force loads on the hybrid rotor in a novel hybrid magnetic-bearing switched-reluctance motor (MBSRM) have been performed. A MBSRM has the combined characteristics of a switched-reluctance motor and a magnetic bearing. The MBSRM discussed in this report has an eight-pole stator and a six-pole hybrid rotor, which is composed of circular and scalloped lamination segments. The hybrid rotor is levitated using only one set of four stator poles, while a second set of four stator poles imparts torque to the scalloped portion of the rotor, which is driven in a traditional switched reluctance manner by a processor. Static torque and radial force analysis were done for rotor poles that were oriented to achieve maximum and minimum radial force loads on the rotor. The objective is to assess whether simple one-dimensional magnetic circuit analysis is sufficient for preliminary evaluation of this machine, which may exhibit strong three-dimensional electromagnetic field behavior. Two magnetic circuit geometries, approximating the complex topology of the magnetic fields in and around the hybrid rotor, were employed in formulating the electromagnetic radial force equations. Reasonable agreement between the experimental and the theoretical radial force loads predictions was obtained with typical magnetic bearing derating factors applied to the predictions
Discovery of a Faint Companion to Alcor Using MMT/AO 5 m Imaging
We report the detection of a faint stellar companion to the famous nearby A5V
star Alcor (80 UMa). The companion has M-band ( = 4.8 m)
magnitude 8.8 and projected separation 1".11 (28 AU) from Alcor. The companion
is most likely a low-mass (0.3 \msun) active star which is responsible
for Alcor's X-ray emission detected by ROSAT (L 10
erg/s). Alcor is a nuclear member of the Ursa Major star cluster (UMa; d
25 pc, age 0.5 Gyr), and has been occasionally mentioned as a
possible distant (709") companion of the stellar quadruple Mizar ( UMa).
Comparing the revised Hipparcos proper motion for Alcor with the mean motion
for other UMa nuclear members shows that Alcor has a peculiar velocity of 1.1
km/s, which is comparable to the predicted velocity amplitude induced by the
newly-discovered companion (1 km/s). Using a precise dynamical parallax
for Mizar and the revised Hipparcos parallax for Alcor, we find that Mizar and
Alcor are physically separated by 0.36 0.19 pc (74 39 kAU; minimum
18 kAU), and their velocity vectors are marginally consistent (
probability 6%). Given their close proximity and concordant motions we suggest
that the Mizar quadruple and the Alcor binary be together considered the 2nd
closest stellar sextuplet. The addition of Mizar-Alcor to the census of stellar
multiples with six or more components effectively doubles the local density of
such systems within the local volume (d 40 pc).Comment: 28 pages, 2 figures, AJ, in press; emulateapj short version at
http://www.pas.rochester.edu/~emamajek/alcor.pd
Why Orange Guaymas Basin Beggiatoa spp. Are Orange: Single-Filament-Genome-Enabled Identification of an Abundant Octaheme Cytochrome with Hydroxylamine Oxidase, Hydrazine Oxidase, and Nitrite Reductase Activities
ABSTRACT Orange, white, and yellow vacuolated Beggiatoaceae filaments are visually dominant members of microbial mats found near sea floor hydrothermal vents and cold seeps, with orange filaments typically concentrated toward the mat centers. No marine vacuolate Beggiatoaceae are yet in pure culture, but evidence to date suggests they are nitrate-reducing, sulfide-oxidizing bacteria. The nearly complete genome sequence of a single orange Beggiatoa (ā Candidatus Maribeggiatoaā) filament from a microbial mat sample collected in 2008 at a hydrothermal site in Guaymas Basin (Gulf of California, Mexico) was recently obtained. From this sequence, the gene encoding an abundant soluble orange-pigmented protein in Guaymas Basin mat samples (collected in 2009) was identified by microcapillary reverse-phase high-performance liquid chromatography (HPLC) nano-electrospray tandem mass spectrometry (Ī¼LCāMS-MS) of a pigmented band excised from a denaturing polyacrylamide gel. The predicted protein sequence is related to a large group of octaheme cytochromes whose few characterized representatives are hydroxylamine or hydrazine oxidases. The protein was partially purified and shown by in vitro assays to have hydroxylamine oxidase, hydrazine oxidase, and nitrite reductase activities. From what is known of Beggiatoaceae physiology, nitrite reduction is the most likely in vivo role of the octaheme protein, but future experiments are required to confirm this tentative conclusion. Thus, while present-day genomic and proteomic techniques have allowed precise identification of an abundant mat protein, and its potential activities could be assayed, proof of its physiological role remains elusive in the absence of a pure culture that can be genetically manipulated
Detection of Two Interstellar Polycyclic Aromatic Hydrocarbons via Spectral Matched Filtering
Ubiquitous unidentified infrared emission bands are seen in many astronomical
sources. Although these bands are widely, if not unanimously, attributed to the
collective emission from polycyclic aromatic hydrocarbons, no single species
from this class has been detected in space. We present the discovery of two -CN
functionalized polycyclic aromatic hydrocarbons, 1- and 2-cyanonaphthalene, in
the interstellar medium aided by spectral matched filtering. Using radio
observations with the Green Bank Telescope, we observe both bi-cyclic ring
molecules in the molecular cloud TMC-1. We discuss potential in situ gas-phase
formation pathways from smaller organic precursor molecules
Immunophenotyping of Circulating and Intratumoral Myeloid and T Cells in Glioblastoma Patients
Glioblastoma is the most common and lethal primary brain malignancy that almost inevitably recurs as therapy-refractory cancer. While the success of immune checkpoint blockade (ICB) revealed the immense potential of immune-targeted therapies in several types of cancers outside the central nervous system, it failed to show objective responses in glioblastoma patients as of now. The ability of glioblastoma cells to drive multiple modes of T cell dysfunction while exhibiting low-quality neoepitopes, low-mutational load, and poor antigen priming limits anti-tumor immunity and efficacy of antigen-unspecific immunotherapies such as ICB. An in-depth understanding of the GBM immune landscape is essential to delineate and reprogram such immunosuppressive circuits during disease progression. In this view, the present study aimed to characterize the peripheral and intratumoral immune compartments of 35 glioblastoma patients compared to age- and sex-matched healthy control probands, particularly focusing on exhaustion signatures on myeloid and T cell subsets. Compared to healthy control participants, different immune signatures were already found in the peripheral circulation, partially related to the steroid medication the patients received. Intratumoral CD4+ and CD8+ TEM cells (CD62Llow/CD45ROhigh) revealed a high expression of PD1, which was also increased on intratumoral, pro-tumorigenic macrophages/microglia. Histopathological analysis further identified high PSGL-1 expression levels of the latter, which has recently been linked to increased metastasis in melanoma and colon cancer via P-selectin-mediated platelet activation. Overall, the present study comprises immunophenotyping of a patient cohort to give implications for eligible immunotherapeutic targets in neurooncology in the future
High-resolution genome-wide cytosine methylation profiling with simultaneous copy number analysis and optimization for limited cell numbers
Many genome-wide assays involve the generation of a subset (or representation) of the genome following restriction enzyme digestion. The use of enzymes sensitive to cytosine methylation allows high-throughput analysis of this epigenetic regulatory process. We show that the use of a dual-adapter approach allows us to generate genomic representations that includes fragments of <200ābp in size, previously not possible when using the standard approach of using a single adapter. By expanding the representation to smaller fragments using HpaII or MspI, we increase the representation by these isoschizomers to more than 1.32 million loci in the human genome, representing 98.5% of CpG islands and 91.1% of refSeq promoters. This advance allows the development of a new, high-resolution version of our HpaII-tiny fragment Enrichment by Ligation-mediated PCR (HELP) assay to study cytosine methylation. We also show that the MspI representation generates information about copy-number variation, that the assay can be used on as little as 10āng of DNA and that massively parallel sequencing can be used as an alternative to microarrays to read the output of the assay, making this a powerful discovery platform for studies of genomic and epigenomic abnormalities
The Deep X-ray Radio Blazar Survey (DXRBS). I. Methods and First Results
We have undertaken a survey of archived, pointed ROSAT PSPC data for blazars
by correlating the ROSAT WGACAT database with several publicly available radio
catalogs, restricting our candidate list to serendipitous flat radio spectrum
sources (alpha_r <= 0.70). Here we discuss our survey methods, identification
procedure and first results. Our survey is found to be ~ 95% efficient at
finding flat-spectrum radio-loud quasars (FSRQs, 59 of our first 85 IDs) and BL
Lacertae objects (22 of our first 85 IDs), a figure which is comparable to or
greater than that achieved by other radio and X-ray survey techniques.
The identifications presented here show that all previous samples of blazars
(even when taken together) did not representatively survey the blazar
population, missing critical regions of (L_X,L_R) parameter space within which
large fractions of the blazar population lie. Particularly important is the
identification of a large population of FSRQs (>~ 25% of DXRBS FSRQs) with
ratios of X-ray to radio luminosity >~ 10^-6 (alpha_rx <~ 0.78). In addition,
due to our greater sensitivity, DXRBS has already more than doubled the number
of FSRQs in complete samples with 5 GHz (radio) luminosities between 10^31.5
and 10^33.5 erg/s/Hz and fills in the region of parameter space between X-ray
selected and radio-selected samples of BL Lacs. DXRBS is the very first sample
to contain statistically significant numbers of blazars at low luminosities,
approaching what should be the lower end of the FSRQ luminosity function.Comment: 34 pages, 7 figures, 6 tables, LaTeX file, uses aaspp4.sty. To appear
in the Astronomical Journa
Communications Biophysics
Contains research objectives and reports on six research projects split into three sections.National Institutes of Health (Grant 5 P01 NS13126-07)National Institutes of Health (Training Grant 5 T32 NS07047-05)National Institutes of Health (Training Grant 2 T32 NS07047-06)National Science Foundation (Grant BNS 77-16861)National Institutes of Health (Grant 5 R01 NS1284606)National Institutes of Health (Grant 5 T32 NS07099)National Science Foundation (Grant BNS77-21751)National Institutes of Health (Grant 5 R01 NS14092-04)Gallaudet College SubcontractKarmazin Foundation through the Council for the Arts at M.I.T.National Institutes of Health (Grant 1 R01 NS1691701A1)National Institutes of Health (Grant 5 R01 NS11080-06)National Institutes of Health (Grant GM-21189
Overview and status of EXCLAIM, the experiment for cryogenic large-aperture intensity mapping
The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a
balloon-borne far-infrared telescope that will survey star formation history
over cosmological time scales to improve our understanding of why the star
formation rate declined at redshift z < 2, despite continued clustering of dark
matter. Specifically,EXCLAIM will map the emission of redshifted carbon
monoxide and singly-ionized carbon lines in windows over a redshift range 0 < z
< 3.5, following an innovative approach known as intensity mapping. Intensity
mapping measures the statistics of brightness fluctuations of cumulative line
emissions instead of detecting individual galaxies, thus enabling a blind,
complete census of the emitting gas. To detect this emission unambiguously,
EXCLAIM will cross-correlate with a spectroscopic galaxy catalog. The EXCLAIM
mission uses a cryogenic design to cool the telescope optics to approximately
1.7 K. The telescope features a 90-cm primary mirror to probe spatial scales on
the sky from the linear regime up to shot noise-dominated scales. The telescope
optical elements couple to six {\mu}-Spec spectrometer modules, operating over
a 420-540 GHz frequency band with a spectral resolution of 512 and featuring
microwave kinetic inductance detectors. A Radio Frequency System-on-Chip
(RFSoC) reads out the detectors in the baseline design. The cryogenic telescope
and the sensitive detectors allow EXCLAIM to reach high sensitivity in spectral
windows of low emission in the upper atmosphere. Here, an overview of the
mission design and development status since the start of the EXCLAIM project in
early 2019 is presented.Comment: SPIE Astronomical Telescopes + Instrumentation. arXiv admin note:
substantial text overlap with arXiv:1912.0711
- ā¦