1,249 research outputs found
Contextual impacts on industrial processes brought by the digital transformation of manufacturing: a systematic review
The digital transformation of manufacturing (a phenomenon also known as "Industry 4.0" or "Smart Manufacturing") is finding a growing interest both at practitioner and academic levels, but is still in its infancy and needs deeper investigation. Even though current and potential advantages of digital manufacturing are remarkable, in terms of improved efficiency, sustainability, customization, and flexibility, only a limited number of companies has already developed ad hoc strategies necessary to achieve a superior performance. Through a systematic review, this study aims at assessing the current state of the art of the academic literature regarding the paradigm shift occurring in the manufacturing settings, in order to provide definitions as well as point out recurring patterns and gaps to be addressed by future research. For the literature search, the most representative keywords, strict criteria, and classification schemes based on authoritative reference studies were used. The final sample of 156 primary publications was analyzed through a systematic coding process to identify theoretical and methodological approaches, together with other significant elements. This analysis allowed a mapping of the literature based on clusters of critical themes to synthesize the developments of different research streams and provide the most representative picture of its current state. Research areas, insights, and gaps resulting from this analysis contributed to create a schematic research agenda, which clearly indicates the space for future evolutions of the state of knowledge in this field
Stochastic gravitational background from inflationary phase transitions
We consider true vacuum bubbles generated in a first order phase transition
occurring during the slow rolling era of a two field inflation: it is known
that gravitational waves are produced by the collision of such bubbles. We find
that the epoch of the phase transition strongly affects the characteristic peak
frequency of the gravitational waves, causing an observationally interesting
redshift in addition to the post-inflationary expansion. In particular it is
found that a phase transition occurring typically 1020 foldings
before the reheating at GeV may be detected by the next Ligo
gravity waves interferometers. Moreover, for recently proposed models capable
of generating the observed large scale voids as remnants of the primordial
bubbles (for which the characteristic wave lengths are several tens of Mpc), it
is found that the level of anisotropy of the cosmic microwave background
provides a deep insight upon the physical parameters of the effective
Lagrangian.Comment: 12 pages, 3 figures. Phys.Rev.D in pres
Constraints on coupled dark energy using CMB data from WMAP and SPT
We consider the case of a coupling in the dark cosmological sector, where a
dark energy scalar field modifies the gravitational attraction between dark
matter particles. We find that the strength of the coupling {\beta} is
constrained using current Cosmic Microwave Background (CMB) data, including
WMAP7 and SPT, to be less than 0.063 (0.11) at 68% (95%) confidence level.
Further, we consider the additional effect of the CMB-lensing amplitude,
curvature, effective number of relativistic species and massive neutrinos and
show that the bound from current data on {\beta} is already strong enough to be
rather stable with respect to any of these variables. The strongest effect is
obtained when we allow for massive neutrinos, in which case the bound becomes
slightly weaker, {\beta} < 0.084(0.14). A larger value of the effective number
of relativistic degrees of freedom favors larger couplings between dark matter
and dark energy as well as values of the spectral index closer to 1. Adding the
present constraints on the Hubble constant, as well as from baryon acoustic
oscillations and supernovae Ia, we find {\beta} < 0.050(0.074). In this case we
also find an interesting likelihood peak for {\beta} = 0.041 (still compatible
with 0 at 1{\sigma}). This peak comes mostly from a slight difference between
the Hubble parameter HST result and the WMAP7+SPT best fit. Finally, we show
that forecasts of Planck+SPT mock data can pin down the coupling to a precision
of better than 1% and detect whether the marginal peak we find at small non
zero coupling is a real effect.Comment: 22 pages, 17 figure
Reconstruction of the bubble nucleating potential
We calculate analytically the bubble nucleation rate in a model of first
order inflation which is able to produce large scale structure. The computation
includes the first-order departure from the thin-wall limit, the explicit
derivation of the pre-exponential factor, and the gravitational correction. The
resulting bubble spectrum is then compared with constraints from the large
scale structure and the microwave background. We show that there are models
which pass all the constraints and produce bubble-like perturbations of
interesting size. Furthermore, we show that it is in principle possible to
reconstruct completely the inflationary two-field potential from observations.Comment: Accepted for publication in Phys. Rev. D, 19 pages, 2 ps figs
include
Branched Spines of 3-Manifolds and Reidemeister Torsion of Euler Structures
We consider homotopy classes of non-singular vector
fields on three-manifolds with boundary and we define for these
classes torsion invariants of Reidemeister type. We show that
torsion is well-defined and equivariant under the action of the appropriate homology group using an elementary and self-contained
technique. Namely, we use the theory of branched standard spines
to express the difference between two homotopy classes as a combination of well-understood elementary catastrophes. As a special
case we are able to reproduce Turaevâs theory of Reidemeister torsion for Euler structures on closed manifolds of dimension three
Spin structures on 3-manifolds via arbitrary triangulations
Let M be an oriented compact 3-manifold and let T be a (loose) triangulation
of M, with ideal vertices at the components of the boundary of M and possibly
internal vertices. We show that any spin structure s on M can be encoded by
extra combinatorial structures on T. We then analyze how to change these extra
structures on T, and T itself, without changing s, thereby getting a
combinatorial realization, in the usual "objects/moves" sense, of the set of
all pairs (M,s). Our moves have a local nature, except one, that has a global
flavour but is explicitly described anyway. We also provide an alternative
approach where the global move is replaced by simultaneous local ones.Comment: 49 pages, many figure
Sub-degree CMB anisotropies from inflationary bubbles
It is well known that processes of first order phase transitions may have
occurred in the inflationary era. If one or more occurred well before the end
of inflation, the nucleated bubbles are stretched to large scales and the
primordial power spectrum contains a scale dependent non-Gaussian component
provided by the remnants of the bubbles. We predict the anisotropies in the
cosmic microwave background (CMB) induced by inflationary bubbles. We build a
general analytic model for describing a bubbly perturbation; we evolve each
Fourier mode using the linear theory of perturbations from reheating until
decoupling; we get the CMB anisotropies by considering the bubbly perturbation
intersecting the last scattering surface. The CMB image of an inflationary
bubble is a series of concentric isothermal rings of different color (sign of
) on the scale of the sound horizon at decoupling ( in
the sky); the resulting anisotropy is therefore strongly non-Gaussian. The mean
amplitude of for a bubble of size follows the known estimates
for linear perturbations, . In particular, bubbles with size corresponding to the seeds of
the observed large scale voids (tens of comoving Mpc) induce an interesting
pattern of CMB anisotropies on the sub-degree angular scale, to be further
investigated and compared with the forthcoming high resolution CMB maps
provided by the MAP and the Planck experiments.Comment: 10 pages, 5 postscript figures, accepted by Ap.
CD3+CD4+LAP+Foxp3-regulatory cells of the colonic lamina propria limit disease extension in ulcerative colitis
Background and Aims: In ulcerative colitis (UC), inflammation begins in the rectum and
can extend proximally throughout the entire colon. The extension of inflammation is an
important determinant of disease course, and may be limited by the action of regulatory
T cells (Tregs). In this cross-sectional study, we evaluated the relationship between UC
extension and the proportions of CD3+CD4+Foxp3+ and CD3+CD4+LAP+Foxp3-
Tregs in the colonic lamina propria (LP) of 79 UC patients and 29 controls. The role of
these cells in UC extension was also investigated in the murine oxazolone-induced colitis
model.
Methods: Patients: Disease extension was classified according to the Montreal
classification. Where possible, endoscopic biopsies of involved and uninvolved
tissue were obtained from UC patients. Mouse model: Colitis was induced by
intrarectal oxazolone administration. Lamina propria mononuclear cells were isolated
from patient biopsies and mouse colon tissue using enzymatic method and the
percentage of CD3+CD4+Foxp3+ and CD3+CD4+LAP+Foxp3-cells evaluated by
immunofluorescence. Confocal microscopy was applied for the visualization and
quantification of CD4+LAP+ cells on tissue histological sections.
Results: In UC patients with distal colitis the proportion of LP CD3+CD4+Foxp3+
Tregs was significantly higher in inflamed tissue than uninvolved tissue. As opposite, the
proportion of LP CD3+CD4+LAP+ Tregs was significantly higher in uninvolved tissue
than involved tissue. Both LP CD3+CD4+Foxp3+ and LP CD3+CD4+LAP+ Tregs
proportion in involved tissue was significantly higher than in controls irrespective of the
extension of inflammation. In mice with oxazolone-induced distal colitis, treatment with
LAP-depleting antibody was associated with the development of extensive colitis.
Conclusions: Our findings suggest that CD3+CD4+LAP+Foxp3-Tregs limit the
extension of inflammatory lesions in UC patients
COVID-19 VACCINES: EVIDENCE, CHALLENGES AND THE FUTURE
Through an unprecedented research and development process, in early 2021, just one year after the COVID-19 pandemic started devastating the world, there are several vaccines commercially available or in advanced phase of testing, each with its own characteristics and challenges. For the first time in the history of vaccination, a global immunization programme has started at a time of intense pandemic activity characterized by high virus transmission, facilitating selection of variants potentially able to escape the vaccine-induced antibody response. The reality is that one cannot rely on a single vaccine when dealing with a pandemic emergency: the urgent need of billions of doses clashes with the production capacity of the pharmaceutical industry. There is therefore no ideal vaccine, but there are many good vaccines to be used immediately. Today, the international debate about COVID-19 vaccines is the hottest topic in global health whether it relates to technical and scientific issues or to the ethical aspects of access to vaccinations for all. This article aims at reviewing the status of vaccines that are used, or about to be used, in immunization campaigns worldwide
Down-regulation of the Lamin A/C in neuroblastoma triggers the expansion of tumor initiating cells
Tumor-initiating cells constitute a population within a tumor mass that shares properties with normal stem cells and is considered responsible for therapy failure in many cancers. We have previously demonstrated that knockdown of the nuclear envelope component Lamin A/C in human neuroblastoma cells inhibits retinoic acid-mediated differentiation and results in a more aggressive phenotype. In addition, Lamin A/C is often lost in advanced tumors and changes in the nuclear envelope composition occur during tumor progression. Based on our previous data and considering that Lamin A/C is expressed in differentiated tissues, we hypothesize that the lack of Lamin A/C could predispose cells toward a stem-like phenotype, thus influencing the development of tumor-initiating cells in neuroblastoma. This paper demonstrates that knockdown of Lamin A/C triggers the development of a tumor-initiating cell population with self-renewing features in human neuroblastoma cells. We also demonstrates that the development of TICs is due to an increased expression of MYCN gene and that in neuroblastoma exists an inverse relationship between LMNA and MYCN expression
- âŠ