17 research outputs found
Mathematical modeling of auxetic systems : bridging the gap between analytical models and observation
The Poissonâs ratio, a property which quantifies the changes in thickness when a material is stretched and
compressed, can be determined as the negative of the transverse strain over the applied strain. In the scientific
literature, there are various ways how strain may be defined and the actual definition used could result in a
different Poissonâs ratio being computed. This paper will look in more detail at this by comparing the more
commonly used forms of strain and the Poissonâs ratio that is computable from them. More specifically, an attempt
is made to assess through examples on the usefulness of the various formulations to properly describe what can
actually be observed, thus providing a clearer picture of which form of Poissonâs ratio should be used in analytical
modelling.peer-reviewe
A novel mechanical metamaterial exhibiting auxetic behavior and negative compressibility
Auxetics (negative Poissonâs ratio) and materials with negative linear compressibility
(NLC) exhibit the anomalous mechanical properties of getting wider rather than thinner when
stretched and expanding in at least one direction under hydrostatic pressure, respectively. A novel
mechanismâtermed the âtriangular elongation mechanismââleading to such anomalous behavior is
presented and discussed through an analytical model. Amongst other things, it is shown that this
novel mechanism, when combined with the well-known ârotating squaresâ model, can generate giant
negative Poissonâs ratios when the system is stretched.peer-reviewe
Auxetic-inspired honeycomb macrostructures with anomalous tailormade thermal expansion properties including ânegativeâ heat-shrinking characteristics
Negative thermal expansion (NTE) materials and structures exhibit the anomalous property
of shrinking rather than expanding when heated. This work examines the potential of multimaterial
planar re-entrant and non-re-entrant honeycombs to exhibit anomalous thermal
expansion properties. Expressions for the coefficient of thermal expansion as a function of
the geometric parameters and intrinsic thermal expansion properties were derived for any
in-plane direction. It was shown that re-entrant honeycombs, a metamaterial which is well
known for its auxetic characteristics, can be made to exhibit NTE in specific directions
when constructed from conventional positive thermal expansion (PTE) materials, provided
that the slanting ligaments expand more than the vertical ligaments when heated and that
the geometry is amenable. Conversely, it was shown that the construction of such
honeycombs from NTE components will not necessarily result in a system which
exhibits NTE in all directions. Furthermore, conditions which result in honeycombs
demonstrating zero thermal expansion (ZTE) coefficients in specific directions were
also explored.peer-reviewe
A Cdh3-β-catenin-laminin signaling axis in a subset of breast tumor leader cells control leader cell polarization and directional collective migration
Carcinoma dissemination can occur when heterogeneous tumor and tumor-stromal cell clusters migrate together via collective migration. Cells at the front lead and direct collective migration, yet how these leader cells form and direct migration are not fully appreciated. From live videos of primary mouse and human breast tumor organoids in a 3D microfluidic system mimicking native breast tumor microenvironment, we developed 3D computational models, which hypothesize that leader cells need to generate high protrusive forces and overcome extracellular matrix (ECM) resistance at the leading edge. From single-cell sequencing analyses, we find that leader cells are heterogeneous and identify and isolate a keratin 14- and cadherin-3-positive subpopulation sufficient to lead collective migration. Cdh3 controls leader cell protrusion dynamics through local production of laminin, which is required for integrin/focal adhesion function. Our findings highlight how a subset of leader cells interact with the microenvironment to direct collective migration
The multidirectional auxeticity and negative linear compressibility of a 3D mechanical metamaterial
In this work, through the use of a theoretical model, we analyse the potential of a specific
three-dimensional mechanical metamaterial composed of arrowhead-like structural units to exhibit
a negative Poissonâs ratio for an arbitrary loading direction. Said analysis allows us to assess its
suitability for use in applications where materials must be able to respond in a desired manner to
a stimulus applied in multiple directions. As a result of our studies, we show that the analysed system
is capable of exhibiting auxetic behaviour for a broad range of loading directions, with isotropic
behaviour being shown in some planes. In addition to that, we show that there are also certain
loading directions in which the system manifests negative linear compressibility. This enhances its
versatility and suitability for a number of applications where materials exhibiting auxetic behaviour
or negative linear compressibility are normally implemented.peer-reviewe
Blisters and calluses from rowing : prevalence, perceptions and pain tolerance
Background and Objectives: Rowing is a sport that involves constant gripping, pulling/pushing,
and rotational movements of the hands, in a cyclic periodic manner with every stroke, with hundreds
of strokes being taken within a short period of time. Dermatological issues on rowersâ hands (fingers
and palms) in the form of blisters and calluses are common knowledge within the community, but
their prevalence and the rowerâs perceptions and pain tolerance to them has never been systematically
evaluated. This work addresses these lacunae. Materials and Methods: Analysis of data collected
from a survey on a sample of competitive (117) and noncompetitive rowers (28) who row on-water
(total 145). Results: It was found that approximately 69% of rowers participating in this study have
calluses on their hands for most of their time (considered by them as not painful). The incidence of
blisters was found to be lower (but perceived as more painful). Their incidence was found to be fairly
independent of the frequency and intensity of training, but they seem to affect most rowers equally at
the beginning of season or during a change of position (nonconditioned hands). Blisters and calluses
were reported to be mainly located on the proximal phalanges and metacarpo-phalangeal joint area
of both hands, i.e., on the lower parts of the fingers and the upper inner palms. Conclusions: Rowers
demonstrated a sense of acceptance of these dermatological issues, even a sense of pride in what they
represent. The incidence of blisters becoming infected was estimated to be so low that most rowers
would not have encountered such serious, albeit rare, consequences.peer-reviewe
Application of CRISPR-Cas9 Gene Editing for HIV Host Factor Discovery and Validation
Human Immunodeficiency Virus (HIV) interacts with a wide array of host factors at each stage of its lifecycle to facilitate replication and circumvent the immune response. Identification and characterization of these host factors is critical for elucidating the mechanism of viral replication and for developing next-generation HIV-1 therapeutic and curative strategies. Recent advances in CRISPR-Cas9-based genome engineering approaches have provided researchers with an assortment of new, valuable tools for host factor discovery and interrogation. Genome-wide screening in a variety of in vitro cell models has helped define the critical host factors that play a role in various cellular and biological contexts. Targeted manipulation of specific host factors by CRISPR-Cas9-mediated gene knock-out, overexpression, and/or directed repair have furthermore allowed for target validation in primary cell models and mechanistic inquiry through hypothesis-based testing. In this review, we summarize several CRISPR-based screening strategies for the identification of HIV-1 host factors and highlight how CRISPR-Cas9 approaches have been used to elucidate the molecular mechanisms of viral replication and host response. Finally, we examine promising new technologies in the CRISPR field and how these may be applied to address critical questions in HIV-1 biology going forward
Host ZCCHC3 blocks HIV-1 infection and production through a dual mechanism
Summary: Most mammalian cells prevent viral infection and proliferation by expressing various restriction factors and sensors that activate the immune system. Several host restriction factors that inhibit human immunodeficiency virus type 1 (HIV-1) have been identified, but most of them are antagonized by viral proteins. Here, we describe CCHC-type zinc-finger-containing protein 3 (ZCCHC3) as a novel HIV-1 restriction factor that suppresses the production of HIV-1 and other retroviruses, but does not appear to be directly antagonized by viral proteins. It acts by binding to Gag nucleocapsid (GagNC) via zinc-finger motifs, which inhibits viral genome recruitment and results in genome-deficient virion production. ZCCHC3 also binds to the long terminal repeat on the viral genome via the middle-folded domain, sequestering the viral genome to P-bodies, which leads to decreased viral replication and production. This distinct, dual-acting antiviral mechanism makes upregulation of ZCCHC3 a novel potential therapeutic strategy
Univariable regression of suture type (absorbable or non-absorbable) on IH rates.
<p><sup>a</sup> Studies with more than one patient group available for analysis.</p><p>Summary Suture type (absorbable versus non-absorbable) had no effect on IH rates.</p><p>Univariable regression of suture type (absorbable or non-absorbable) on IH rates.</p