7,142 research outputs found
Evaluation of Coulomb potential in a triclinic cell with periodic boundary conditions
Lekner and Sperb's work on the evaluation of Coulomb energy and forces under
periodic boundary conditions is generalized that makes it possible to use a
triclinic unit cell in simulations in 3D rather than just an orthorhombic cell.
The expressions obtained are in a similar form as previously obtained by Lekner
and Sperb for the especial case of orthorhombic cell
Learning General Purpose Distributed Sentence Representations via Large Scale Multi-task Learning
A lot of the recent success in natural language processing (NLP) has been
driven by distributed vector representations of words trained on large amounts
of text in an unsupervised manner. These representations are typically used as
general purpose features for words across a range of NLP problems. However,
extending this success to learning representations of sequences of words, such
as sentences, remains an open problem. Recent work has explored unsupervised as
well as supervised learning techniques with different training objectives to
learn general purpose fixed-length sentence representations. In this work, we
present a simple, effective multi-task learning framework for sentence
representations that combines the inductive biases of diverse training
objectives in a single model. We train this model on several data sources with
multiple training objectives on over 100 million sentences. Extensive
experiments demonstrate that sharing a single recurrent sentence encoder across
weakly related tasks leads to consistent improvements over previous methods. We
present substantial improvements in the context of transfer learning and
low-resource settings using our learned general-purpose representations.Comment: Accepted at ICLR 201
Physiological and behavioural aspects of housing stress in cattle
End of project reportThe effect of various space allowances on pituitary, adrenal, immune responses and performance was investigated in 72 Holstein x Friesian bulls. Bulls (403 ± 3.5 kg) were blocked by weight and randomly assigned into two groups (familiar, F and unfamiliar, UF) x three (1.2, 2.7 and 4.2 m2 per bull; n = 24 bulls per space allowance) treatments and housed for 83 days in 18 pens (n = 4 per pen). Blood samples were collected on day –1, 0, 3, 14, 36 and 77 with respect to mixing and housing on day 0. The bulls were administered with adrenocorticotrophic hormone (ACTH) on day 3 and corticotrophin-releasing hormone (CRH) on days 14, 36 and 77. The basal cortisol concentrations were not affected (P>0.05) by mixing of familiar and unfamiliar bulls. On day 3, basal cortisol was greater (P0.05) of treatment and treatment x time on ACTH. On day 14, interferon-? production was lower (P0.05) different for those housed at 1.2 m2. Bulls housed at either space allowances had (P<0.05) neutrophilia, lymphopenia, eosinopenia and decreased haemoglobin on day 3 compared with day 0. The liveweight gain from days 0 to 83 was lower (P< 0.05) in bulls housed at 1.2 compared with those at 2.7 and 4.2 m2. Housing bulls at 1.2 m2 space allowance had a detrimental effect on their growth and was associated with an acute rise in plasma cortisol concentration (on day 3) compared with space allowances of 2.7 and 4.2 m2/bull.European Union Structural Funds (EAGGF
Structural characterization of carbon nanotubes via the vibrational density of states
The electrical and chemical properties of carbon nanotubes vary significantly
with different chirality and diameter, making the experimental determination of
these structural properties important. Here, we show that the vibrational
density of states (VDOS) contains information on the structure of carbon
nanotubes, particularly at low frequencies. We show that the diameter and
chirality of the nanotubes can be determined from the characteristic low
frequency and modes in the VDOS. For zigzag nanotubes, the peak
splits into two peaks giving rise to another low energy peak. The
significant changes in the frequencies and relative intensities of these peaks
open up a route to distinguish among structurally different nanotubes. A close
study of different orientations of Stone-Wales defects with varying defect
density reveals that different structural defects also leave distinct
fingerprints in the VDOS, particularly in the and modes. With our
results, more structural information can be obtained from experiments which can
directly measure the VDOS, such as inelastic electron and inelastic neutron
spectroscopy.Comment: 5 Figures, Accepted for publication in Carbo
Effective way to sum over long range Coulomb potentials in two and three dimensions
I propose a method to calculate logarithmic interaction in two dimensions and
coulomb interaction in three dimensions under periodic boundary conditions.
This paper considers the case of a rectangular cell in two dimensions and an
orthorhombic cell in three dimensions. Unlike the Ewald method, there is no
parameter to be optimized, nor does it involve error functions, thus leading to
the accuracy obtained. This method is similar in approach to that of Sperb [R.
Sperb, Mol. Simulation, 22, 199 (1999).], but the derivation is considerably
simpler and physically appealing. An important aspect of the proposed method is
the faster convergence of the Green function for a particular case as compared
to Sperb's work. The convergence of the sums for the most part of unit cell is
exponential, and hence requires the calculation of only a few dozen terms. In a
very simple way, we also obtain expressions for interaction for systems with
slab geometries. Expressions for the Madelung constant of CsCl and NaCl are
also obtained.Comment: To appear in Phy. Rev.
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Embryonic POU5F1 is Required for Expanded Bovine Blastocyst Formation.
POU5F1 is a transcription factor and master regulator of cell pluripotency with indispensable roles in early embryo development and cell lineage specification. The role of embryonic POU5F1 in blastocyst formation and cell lineage specification differs between mammalian species but remains completely unknown in cattle. The CRISPR/Cas9 system was utilized for targeted disruption of the POU5F1 gene by direct injection into zygotes. Disruption of the bovine POU5F1 locus prevented blastocyst formation and was associated with embryonic arrest at the morula stage. POU5F1 knockout morulas developed at a similar rate as control embryos and presented a similar number of blastomeres by day 5 of development. Initiation of SOX2 expression by day 5 of development was not affected by lack of POU5F1. On the other hand, CDX2 expression was aberrant in embryos lacking POU5F1. Notably, the phenotype observed in bovine POU5F1 knockout embryos reveals conserved functions associated with loss of human embryonic POU5F1 that differ from Pou5f1- null mice. The similarity observed in transcriptional regulation of early embryo development between cattle and humans combined with highly efficient gene editing techniques make the bovine a valuable model for human embryo biology with expanded applications in agriculture and assisted reproductive technologies
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