1,661 research outputs found
Non-random chromosome positioning in mammalian sperm nuclei, with migration of the sex chromosomes during late spermatogenesis
Chromosomes are highly organized and
compartmentalized in cell nuclei. The analysis of their
position is a powerful way to monitor genome organization
in different cell types and states. Evidence suggests that the
organization of the genome could be functionally important
for influencing different cellular and developmental
processes, particularly at early stages of development (i.e.
fertilization and the consequent entry of the sperm nucleus
into the egg). The position of chromosomes in the sperm
nucleus might be crucial, because their location could
determine the time at which particular chromatin domains
are decondensed and remodelled, allowing some epigenetic
level of control or influence over subsequent paternal gene
expression in the embryo. Here, we analyse genome
organization by chromosome position in mammalian
sperm nuclei from three breeds of pig, as a model species.
We have mapped the preferential position of all
chromosomes (bar one) in sperm nuclei in two dimensions
and have established that the sex chromosomes are the
most internally localized chromosomes in mature sperm.
The distribution of two autosomes and chromosomes X and
Y in sperm heads was compared in primary and secondary
spermatocytes and spermatids in porcine testes. The sex
chromosomes were found at the nuclear edge in primary
spermatocytes, which correlates with the known position of
the XY body and their position in somatic cells, whereas,
in spermatids, the sex chromosomes were much more
centrally located, mirroring the position of these
chromosomes in ejaculated spermatozoa. This study
reveals the temporal repositioning of chromosome
territories in spermatogenesis
Implementation of a Direct-Imaging and FX Correlator for the BEST-2 Array
A new digital backend has been developed for the BEST-2 array at
Radiotelescopi di Medicina, INAF-IRA, Italy which allows concurrent operation
of an FX correlator, and a direct-imaging correlator and beamformer. This
backend serves as a platform for testing some of the spatial Fourier transform
concepts which have been proposed for use in computing correlations on
regularly gridded arrays. While spatial Fourier transform-based beamformers
have been implemented previously, this is to our knowledge, the first time a
direct-imaging correlator has been deployed on a radio astronomy array.
Concurrent observations with the FX and direct-imaging correlator allows for
direct comparison between the two architectures. Additionally, we show the
potential of the direct-imaging correlator for time-domain astronomy, by
passing a subset of beams though a pulsar and transient detection pipeline.
These results provide a timely verification for spatial Fourier transform-based
instruments that are currently in commissioning. These instruments aim to
detect highly-redshifted hydrogen from the Epoch of Reionization and/or to
perform widefield surveys for time-domain studies of the radio sky. We
experimentally show the direct-imaging correlator architecture to be a viable
solution for correlation and beamforming.Comment: 12 pages, 17 figures, 2 tables, Accepted to MNRAS January 24, 2014,
includes appendix diagram
Portland State University School of Business Administration (SBA) Renovation + Personal Comfort Investigation
This poster discusses the results of a field study about indoor thermal comfort, based on investigations in Portland State University`s School of Business (SBA) classrooms. The field study was conducted by physical parameter monitoring and questionnaires. Both field monitoring and occupant surveys were performed at the same time during the regular class period.The measurement campaign consisted of measuring the environmental parameters such as temperature (Ta), relative humidity (RH), CO2, and sound levels. The outdoor air temperature, humidity, and sound were registered every 2 hour period during class time. The intention for this project is to investigate thermal comfort of occupants by survey and compare that with the monitored indoor thermal comfort of the occupants. This could assist designers in measuring the energy needed to provide adequate thermal comfort. The results show that classrooms are nearly in a comfort zone and based on the location of the classrooms in the SBA the comfort level is different and students responds differently. The first significant goal in this project is to use these data to decrease the amount of energy that is used in this building by applying new methods in the renovation of these classrooms. The design group intends to execute passive strategies to reach this goal. The second goal is to enhance the educational environment, in terms of thermal conditions, to help students to be more focused on the subjects in the classrooms
Fast Radio Burst 121102 Pulse Detection and Periodicity: A Machine Learning Approach
We report the detection of 72 new pulses from the repeating fast radio burst
FRB 121102 in Breakthrough Listen C-band (4-8 GHz) observations at the Green
Bank Telescope. The new pulses were found with a convolutional neural network
in data taken on August 26, 2017, where 21 bursts have been previously
detected. Our technique combines neural network detection with dedispersion
verification. For the current application we demonstrate its advantage over a
traditional brute-force dedis- persion algorithm in terms of higher
sensitivity, lower false positive rates, and faster computational speed.
Together with the 21 previously reported pulses, this observa- tion marks the
highest number of FRB 121102 pulses from a single observation, total- ing 93
pulses in five hours, including 45 pulses within the first 30 minutes. The
number of data points reveal trends in pulse fluence, pulse detection rate, and
pulse frequency structure. We introduce a new periodicity search technique,
based on the Rayleigh test, to analyze the time of arrivals, with which we
exclude with 99% confidence pe- riodicity in time of arrivals with periods
larger than 5.1 times the model-dependent time-stamp uncertainty. In
particular, we rule out constant periods >10 ms in the barycentric arrival
times, though intrinsic periodicity in the time of emission remains plausible.Comment: 32 pages, 10 figure
Multicolour interphase cytogenetics: 24 chromosome probes, 6 colours, 4 layers
From the late 1980s onwards, the use of DNA probes to visualise sequences on individual chromosomes (fluorescent in-situ hybridisation - FISH) revolutionised the study of cytogenetics. Following single colour experiments, more fluorochromes were added, culminating in a 24 colour assay that could distinguish all human chromosomes. Interphase cytogenetics (the detection of chromosome copy number in interphase nuclei) soon followed, however 24 colour experiments are hampered for this application as mixing fluorochromes to produce secondary colours produces images that are not easily distinguishable from overlapping signals. This study reports the development and use of a novel protocol, new fast hybridising FISH probes, and a bespoke image capture system for the assessment of chromosome copy number in interphase nuclei. The multicolour probe sets can be used individually or in sequential hybridisation layers to assess ploidy of all 24 human chromosomes in the same nucleus. Applications of this technique are in the investigation of chromosome copy number and the assessment of nuclear organisation for a range of different cell types including human sperm, cancer cells and preimplantation embryos
Reachability Aware Capture Regions with Time Adjustment and Cross-Over for Step Recovery
For humanoid robots to live up to their potential utility, they must be able
to robustly recover from instabilities. In this work, we propose a number of
balance enhancements to enable the robot to both achieve specific, desired
footholds in the world and adjusting the step positions and times as necessary
while leveraging ankle and hip. This includes improving the calculation of
capture regions for bipedal locomotion to better consider how step constraints
affect the ability to recover. We then explore a new strategy for performing
cross-over steps to maintain stability, which greatly enhances the variety of
tracking error from which the robot may recover. Our last contribution is a
strategy for time adaptation during the transfer phase for recovery. We then
present these results on our humanoid robot, Nadia, in both simulation and
hardware, showing the robot walking over rough terrain, recovering from
external disturbances, and taking cross-over steps to maintain balance.Comment: Submitted to 2023 IEEE International Conference on Humanoid Robotics
(Humanoids
Environmental safety of entomopathogenic nematodes – Effects on abundance, diversity and community structure of non-target beetles in a forest ecosystem
The large pine weevil, Hylobius abietis, is a serious threat to reforestation in Europe that necessitates routine
use of chemical insecticides. Application of entomopathogenic nematodes (EPN) to the coniferous
tree stumps in which weevils breed has the potential to reduce the use of chemical pesticides. During
field trials to assess the efficacy of nematodes against pine weevil, non-target beetles were also identified
and quantified on 10 sites (14 trials). Nematodes were applied to stumps between June and July. Emergence
traps captured beetles exiting from nematode-treated and untreated control stumps. Four trials
were monitored in the months immediately following nematode application and ten were monitored
the year after nematode application.
A total of 65 species of non-target beetles were recovered, including 11 saproxylic species. We found no
evidence of an effect of applied EPN on non-target beetle species richness, abundance, species richness
per individual collected, or Shannon’s entropy (H’) either immediately or a year after nematode application,
when more wood-specialists were recorded. As expected, there were marked differences between
sites and/or tree species in the populations of non-target beetles recovered.
These results indicate that when EPN are applied in a forest ecosystem to suppress H. abietis populations,
the risk to non-target coleopteran populations must be considered negligible
An analysis of the local causes and effects of AGN produced jets in galaxies at z~2-3.5
We investigate the radio, X-Ray and far-infrared properties of active galactic nuclei (AGN) with strong radio jets at 2.2 0 and average of 0.41±0.21, higher than the average for AGN without jets of 0.14±0.47. We conclude that the presence of jets may inhibit the AGN’s current activity, due to the large size and luminosity of jets, the energy and matter distributions are altered in such a way that the galaxy’s SFR and BHAR are impacted noticeably, agreeing with previous research and findings
New SETI Sky Surveys for Radio Pulses
Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here
we review two of the newest efforts, Astropulse and Fly's Eye.
A variety of possible sources of microsecond to millisecond radio pulses have
been suggested in the last several decades, among them such exotic events as
evaporating primordial black holes, hyper-flares from neutron stars, emissions
from cosmic strings or perhaps extraterrestrial civilizations, but to-date few
searches have been conducted capable of detecting them.
We are carrying out two searches in hopes of finding and characterizing these
mu-s to ms time scale dispersed radio pulses. These two observing programs are
orthogonal in search space; the Allen Telescope Array's (ATA) "Fly's Eye"
experiment observes a 100 square degree field by pointing each 6m ATA antenna
in a different direction; by contrast, the Astropulse sky survey at Arecibo is
extremely sensitive but has 1/3,000 of the instantaneous sky coverage.
Astropulse's multibeam data is transferred via the internet to the computers of
millions of volunteers. These computers perform a coherent de-dispersion
analysis faster than the fastest available supercomputers and allow us to
resolve pulses as short as 400 ns. Overall, the Astropulse survey will be 30
times more sensitive than the best previous searches. Analysis of results from
Astropulse is at a very early stage.
The Fly's Eye was successfully installed at the ATA in December of 2007, and
to-date approximately 450 hours of observation has been performed. We have
detected three pulsars and six giant pulses from the Crab pulsar in our
diagnostic pointing data. We have not yet detected any other convincing bursts
of astronomical origin in our survey data. (Abridged)Comment: 9 pages, 6 figures, Accepted to Acta Astronautica "Special Issue:
Life Signatures
Current and Nascent SETI Instruments
Here we describe our ongoing efforts to develop high-performance and
sensitive instrumentation for use in the search for extra-terrestrial
intelligence (SETI). These efforts include our recently deployed Search for
Extraterrestrial Emissions from Nearby Developed Intelligent Populations
Spectrometer (SERENDIP V.v) and two instruments currently under development;
the Heterogeneous Radio SETI Spectrometer (HRSS) for SETI observations in the
radio spectrum and the Optical SETI Fast Photometer (OSFP) for SETI
observations in the optical band. We will discuss the basic SERENDIP V.v
instrument design and initial analysis methodology, along with instrument
architectures and observation strategies for OSFP and HRSS. In addition, we
will demonstrate how these instruments may be built using low-cost, modular
components and programmed and operated by students using common languages, e.g.
ANSI C.Comment: 12 pages, 5 figures, Original version appears as Chapter 2 in "The
Proceedings of SETI Sessions at the 2010 Astrobiology Science Conference:
Communication with Extraterrestrial Intelligence (CETI)," Douglas A. Vakoch,
Edito
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