text:
In situ formation, manipulation, and imaging of droplet-encapsulated fibrin networks.
ABSTRACT The protein fibrin plays a principal role in blood clotting and forms robust three dimensional networks. Here, microfluidic devices have been tailored to strategically generate and study these bionetworks by confinement in nanoliter volumes. The required protein components are initially encapsulated in separate droplets, which are subsequently merged by electrocoalescence. Next, distinct droplet microenvironments are created as the merged droplets experience one of two conditions: either they traverse a microfluidic pathway continuously, or they "park" to fully evolve an isotropic network before experiencing controlled deformations. High resolution fluorescence microscopy is used to image the fibrin networks in the microchannels. Aggregation (i.e."clotting") is significantly affected by the complicated flow fields in moving droplets. In stopped-flow conditions, an isotropic droplet-spanning network forms after a suitable ripening time. Subsequent network deformation, induced by the geometric structure of the microfluidic channel, is found to be elastic at low rates of deformation. A shape transition is identified for droplets experiencing rates of deformation higher than an identified threshold value. In this condition, significant densification of protein within the droplet due to hydrodynamic forces is observed. These results demonstrate that flow fields considerably affect fibrin in different circumstances exquisitely controlled using microfluidic tools.
Article: Dynamics of counterion-induced attraction between vimentin filaments followed in microfluidic drops.
[Show abstract] [Hide abstract]
ABSTRACT: Intermediate filaments (IFs) are fiber-forming proteins and part of the cytoskeleton of eukaryotes. In vitro the network formation of purified IF systems is mediated, for example, by the interaction with multivalent ions. The understanding of these interaction mechanisms increases the knowledge of the cytoskeleton on a fundamental level. Here, we employ time-lapse fluorescence microscopy to directly image the evolution of network formation of vimentin IFs upon addition of divalent ions. We are thus able to follow the process starting a few seconds after the first encounter of free filaments and ions up to several minutes when the networks are in equilibrium. The local protein density in the compacted networks can reach a factor of 45 higher than the original solution concentration. The competition between mono- and divalent ion condensation onto the protein explains our observations and reveals the polyelectrolyte nature of vimentin as a reason for the protein attraction in the presence of small cations. The method for time-lapse studies in microfluidic drops presented here can be generalized to other dynamic systems.Lab on a Chip 05/2014; · 5.70 Impact Factor - Sonia Mellouli, Begoña Monterroso, Hanumantha Rao Vutukuri, Esra te Brinke, Venkatachalam Chokkalingam, Germán Rivas, Wilhelm T. S. Huck[Show abstract] [Hide abstract]
ABSTRACT: We report a microfluidic approach to generate aqueous droplets in oil of different dimensionality, stabilized by a lipid monolayer, to systematically probe the polymerization of bacterial cell-division protein FtsZ into fibrous networks as a function of the concentrations of crowding agent, FtsZ, and GTP. FtsZ bundles confined in droplets were dynamic, and their distribution depended on the intrinsic properties of the system and restrictions imposed by the spatial boundaries.Soft Matter 01/2013; 9(44):10493. · 4.15 Impact Factor - [Show abstract] [Hide abstract]
ABSTRACT: The flow topology in moving microdroplets has a significant impact on the behaviour of encapsulated objects and hence on applications of the technology. This study reports on a systematic investigation of the flow field inside droplets moving in a rectangular microchannel, by means of micro-particle image velocimetry (µPIV). Various water/oil (w/o) fluid mixtures were studied in order to elucidate the effects of a number of parameters such as capillary number (Ca), droplet geometry, viscosity ratio and interfacial tension. A distinct change in flow topology was observed at intermediate Ca ranging from 10-3 to 10-1, in surfactant-laden droplets, which was attributed primarily to the viscosity ratio of the two phases rather than the Marangoni effect expected in such systems. W/o droplet systems of lower inner-to-outer viscosity ratios tend to exhibit the well-known flow pattern characterised by a parabola-like profile in the droplet bulk-volume, surrounded by two counter rotating recirculation zones on either side of the droplet axis. As the viscosity ratio between the two phases is increased, the flow pattern becomes more uniform, exhibiting low velocities in the droplet bulk-volume and higher-reversed velocities along the w/o interface. The Ca and droplet geometry had no effect on the observed flow topology change. The study highlights the complex, three-dimensional (3D) nature of the flow inside droplets in rectangular microchannels and demonstrates the ability to control the droplet flow environment by adjusting the viscosity ratio between the two phases.Lab on a Chip 07/2014; · 5.70 Impact Factor
Page 1
In situ formation, manipulation, and imaging of droplet-encapsulated fibrin
Heather M. Evans,aEnkhtuul Surenjav,aCraig Priest,abStephan Herminghaus,aRalf Seemannac
and Thomas Pfohl*ad
Received 17th November 2008, Accepted 13th March 2009
First published as an Advance Article on the web 30th March 2009
DOI: 10.1039/b820511f
The protein fibrin plays a principal role in blood clotting and forms robust three dimensional networks.
Here, microfluidic devices have been tailored to strategically generate and study these bionetworks by
confinement in nanoliter volumes. The required protein components are initially encapsulated in
separate droplets, which are subsequently merged by electrocoalescence. Next, distinct droplet
microenvironments are created as the merged droplets experience one of two conditions: either they
traverse a microfluidic pathway continuously, or they ''park'' to fully evolve an isotropic network
before experiencing controlled deformations. High resolution fluorescence microscopy is used to image
the fibrin networks in the microchannels. Aggregation (i.e. ''clotting'') is significantly affected by the
complicated flow fields in moving droplets. In stopped-flow conditions, an isotropic droplet-spanning
network forms after a suitable ripening time. Subsequent network deformation, induced by the
geometric structure of the microfluidic channel, is found to be elastic at low rates of deformation. A
shape transition is identified for droplets experiencing rates of deformation higher than an identified
threshold value. In this condition, significant densification of protein within the droplet due to
hydrodynamic forces is observed. These results demonstrate that flow fields considerably affect fibrin in
different circumstances exquisitely controlled using microfluidic tools.
Microfluidic tools hold great promise in nanotechnology.
Reduced sample volumes, advanced sample handling, and high
throughput dramatically increase the productivity of bioassays
and combinatorial chemical reactions.1,2The ability to generate
precise sample aliquots as droplets in an immiscible continuous
phase enables new schemas involving fluid compartments of
picoliter volumes.3–5Experiments on this scale allow finer control
in studies of complex biomolecular processes and provide a more
efficient and cost-effective experimental design. Furthermore, the
use of microfluidic tools has facilitated investigations into the
evolutionof biomolecularinteractions,
measurements of the early stages of protein folding,6single actin
filament confinement,7and DNA self-assembly processes.8
This study of fibrin is motivated by the protein's biological
relevance and attractive network-forming properties. Fibrin
forms via the assembly of subunits of fibrinogen under conditions
that dictate the physical properties of the network formed.
Hemostasis, or healing of injured blood vessels via blood clot-
ting, is initiated by the aggregation of platelets, which are small
anucleardisksproduced in
as evidenced by
aggregation at the injury site is then aided by the presence of
fibrin. In some cases aggregation can also be detrimental, such as
when foreign therapeutic scaffolds induce the formation of
excessive blood clots.9The biodegradable nature and good tissue
tolerance of fibrin networks have already been demonstrated in
terms of commercially available wound covering agents. In
addition, there is much interest in the deactivation of hemostasis
with respect to artherosclerosis,10inflammation-induced coagu-
lation,11nervous system diseases such as multiple sclerosis,12and
certain cancers.13In addition, from a materials point of view
single fibers of fibrin have been found to show remarkable elas-
ticity.14Looked at as a three-dimensional gel, fibrin networks
display a high elastic modulus that increases with increasing
strain (i.e. strain-stiffen).15This is similar to other biopolymer
networks, but fibrin formation is relatively straightforward and
more reproducible in comparison to other biomaterials: using
only two components, an effectively crosslinked network can
easily be formed.
The building blocks of fibrin are the monomeric protein,
fibrinogen, which comprise about four percent of the total
protein in blood plasma. Each fibrinogen molecule has a length
of 45 nm, and consists of a central domain flanked on either end
by coiled-coil regions. Although the in vivo process of blood
clotting involves a multi-step biological pathway, a minimal
system consists of the protein ''monomers'' of fibrinogen and the
serine protease thrombin (see figure 1). A three-dimensional
fibrin network is initially catalyzed by the presence of thrombin,
which selectively cleaves fibrinopeptides located in the central
domain of fibrinogen. This cleavage creates activated fibrinogen
molecules that reassemble into protofibrils via knob-hole
aMax Planck Institute for Dynamics & Self-Organization, Bunsenstraße
10, 37073 G€ ottingen, Germany
bIan Wark Research Institute, ARC Special Research Centre for Particle
and Material Interfaces, University of South Australia, Mawson Lakes,
South Australia, 5095, Australia
cExperimental PhysicsDepartment,
Saarbr€ ucken, Germany
dDepartment of Chemistry, University of Basel, 4056 Basel, Switzerland
Saarland University,66041,
This journal is ª The Royal Society of Chemistry 2009Lab Chip, 2009, 9, 1933–1941 | 1933
PAPER www.rsc.org/loc | Lab on a Chip
Page 2
interactions. In this sense, the protofibrils can be considered as
''sticky'' objects. Subsequent aggregation of nearby fibrils results
in fibers of thicknesses thoughtto be limited bythe twisting of the
fibers.16Due to this growth and the branching of fibers, a three-
dimensional network is formed that spans micrometers, with
properties that depend on salt and thrombin concentration.17–20
Due to its biological and material relevance, fibrin has been
intensely probed using a variety of techniques. Previous studies
of fibrin formation have used bulk measurements, such as optical
density or light scattering, to characterize fibrin gels.17–19,21
Historically, most microscopy of fibrin networks in the literature
resulted from electron microscopy measurements, which require
staining and fixing of samples in processes that may alter the
native structures.22–24While all of these previous studies have
made important contributions to the understanding of fibrin
formation, there is a dearth of direct measurements of fibrin in its
natural state. Recent measurements suggest that the use of high
resolution light microscopy provides information about the
network that correlates well with some macroscopic measure-
ments, such as turbidity assays.25However, the intrinsic sticki-
ness of fibrin clots is a significant obstacle to their controlled
study in dynamic environments.
The use of microfluidic devices allows for a real-time, direct
measurement of the assembly of fibrin gels under well-controlled
conditions. Furthermore, the implementation of microfluidic
droplets enables the in situ formation, manipulation, and visu-
alization of fibrin networks in a manner that was previously
inaccessible. The systems reported here take advantage of the
microfluidic generation of small volumes of proteins and
enzymes to create an enclosed three-dimensional protein micro-
environment. Rather than focusing on high throughput appli-
cations, high resolution microscopy is utilized to characterize the
finer aspects of fibrin network formation and its behavior within
the microenvironment. Ismagilov et al. showed the feasibility of
microfluidics to determine drug dosages based on blood clotting
times in droplets in a high-throughput approach.26In contrast,
the work reported here focuses on details of the network
formation within a droplet and elucidates the influence of the
microflow and confinement on the protein network.
In order to investigate the evolution and manipulation of this
robust network, we developed microfluidic chips that are capable
of initiating fibrin network formation within droplets. This is
achieved via targeted electrocoalescence between adjacent
droplets and allows the early stages of the fibrin network to be
observed directly. The use of droplets prohibits strong adhesion
of fibrin to the microchannel walls during network formation by
encapsulating the protein and enzyme within the dispersedphase.
Furthermore, the incorporation of geometric structures into the
microchannels enables the controlled deformation of individual
droplets containing fibrin networks. Here, we demonstrate two
types of devices: one in which an evolution to large-scale clotting
is observed, and another in which the elastic network behavior is
determined based on the rate of deformation.
Materials and methods
SU8 microchips
Microchannels were fabricated directly in SU8 photoresist using
UV-photolithography, resulting in a final device as shown in
figure 2. All photolithography solutions were purchased from
Micro Resist Technology GmbH, Germany. Glass disks (50 mm
diameter, VWR) were precoated with Omnicoat and a 5 mm thick
layer of SU8-2005, then exposed to UV radiation and treated in
plasma for 30 seconds to render the surface hydrophilic. After-
wards, SU8-50 was spin-coated to a thickness of 30–40 mm, soft-
baked, and exposed to UV for 30 seconds in the presence of
a photomask containing the desired microchannel structures.
After a post-exposure bake, the glass was rinsed in developer
until the channels were cleared of material. Inlets were drilled
through the glass plate and the channels were closed by thermally
bonding a 50 mm diameter round cover glass (VWR) at 160?C in
a mechanical press. Prior to bonding, gold electrodes and an
underlying chromium adhesion layer were thermally vapor
deposited at 10?6mbar ontothe coverglass and covered by a very
thin bonding layer of PMMA, which was spin coated and baked
onto the cover glass. Wires were glued to the electrodes using
conducting epoxy in order to apply an electric potential during
experiments. Teflon tubing was connected to the microchip via
Nanoports? (UpChurch), which were bonded to the microchip
Fig. 1
scales at each stage in formation.
Hierarchical self-assembly of fibrin, with approximate length
Fig. 2SU8 microchip with ports, tubing, and electrodes.
1934 | Lab Chip, 2009, 9, 1933–1941This journal is ª The Royal Society of Chemistry 2009
Page 3
according to the company protocol. The tubing was connected to
Hamilton microsyringes that were driven using custom-made
pumps controlled by programs written in LabView (National
Instruments Corporation). Additional to the devices described in
this manuscript, similar processes were used to manufacture
a microchip with a much wider chamber in order to stop the large
scale motion of droplets and study the network formation in
what we refer to as ''stopped flow.''
Human fibrinogen (plasminogen, von Willebrand factor, and
fibronectin depleted) was reconstituted in water to a concentra-
tion of 45 mM according to the supplier's guidelines (Enzyme
Research Laboratories, UK). Fluorescent fibrinogen Alexa
Fluor? 546 conjugate was also prepared according to guidelines,
to a concentration of 4.4 mM (Mobitec GmbH). Fibrinogen and
fluorescent fibrinogen were diluted 10:1 in a fibrinogen buffer (20
mM Sodium Citrate-HCl, pH 7.4). Human a-Thrombin, activity
approximately 3000 NIH u/mg (Enzyme Research Laboratories,
UK), was reconstituted in water to a concentration of 94.6 mM
and further diluted in thrombin buffer (50 mM Sodium Citrate,
0.2 M NaCl, 0.1% PEG-10,000, pH 6.5). Relative molar ratios of
fibrinogen to thrombin are given in the text as [F]/[T]. For
comparative studies of beads in droplets, Fluoresbrite? carboxy
NYO 0.50 mm microspheres (Polysciences, Inc., Warrington PA)
were diluted 1:1000 in thrombin solution and flowed through the
microchip as usual.
Imaging and analysis
The droplets were imaged using a Zeiss Axiovert 135 microscope
with a 60? 1.25 NA oil objective and an ebx75 Xenon illumi-
nation source equipped with the appropriate filters to perform
fluorescence experiments using an excitation wavelength of
around 546 nm. Images were recorded using a PCO sensicamQE
camera and CamWare software. Shorter exposure times (typi-
cally, about 700 ms) were required to image fibrin in the serpen-
tine device, and longer times (up to 10 ms) were used in the device
with geometric confinements located after a reaction chamber.
Generally speaking, image contrast and fiber network resolution
were considerably improved with longer exposure times. There-
fore, the longest exposure time possible (considering the experi-
mental restriction of droplet velocity) was always chosen.
Further analysis was conducted for three to five images per data
point using ImageJ image processing software.27
Results and discussion
Droplet formation and fibrin gelation in droplets
Droplets of fibrinogen and thrombin solutions were formed in
a continuous oil phase consisting of a low viscosity organic oil
(Isopar?M, Exxon Mobil). In order to stabilize the emulsion,
a non-ionic surfactant (2 wt% Span? 80, Sigma Aldrich) was
added to the continuous phase. As shown in figure 3, the device
contains two T-junction configurations where the droplets of the
dispersed phase (in this case, protein solution) are formed.28,29As
the stream of the dispersed phase penetrates into the main
channel, a droplet develops. The pressure gradient and shear
force generated by the continuous phase distort the droplet in the
downstream direction until the neck of the dispersed phase thins
and breaks into a droplet (inset, upper left, figure 3).
Under ideal synchronized conditions, droplets from each
T-junction pair together at the following Y-intersection in the
device. The two droplets pass through the electrodes very near to
one another (inset, upper right, figure 3). An applied potential
(10 V, 50 Hz) causes two neighboring droplets to coalesce due to
an electric-field induced instability.30
Clotting in droplets
In order to visualize the formation of fibrin, a microchip incor-
porating serpentine channels was designed. This allows the newly
coalesced droplet, containing fibrinogen and thrombin, to fully
evolve into a fibrin network over the extended length of the
microchannel. The microscope remained in a fixed position on
the device for these experiments. A high magnification objective
(60?) was required to visualize the network in sufficient detail
and, as a result, the camera field of view was only large enough to
image one single droplet at a time. Imaging was carried out at
a number of fixed positions along the serpentine microchannel to
analyze the fibrin networks at various timepoints. Representative
images are shown in figure 4 for droplets prepared at a molar
ratio of fibrinogen to thrombin [F]/[T] ¼ 0.5 and a droplet
velocity v ¼ 5 mm/s. The onset of mixing of the two solutions,
seen in figure 4a, is especially clear since the fibrinogen is fluo-
rescent and the thrombin is not. Shortly after droplet coales-
cence, a homogeneous distribution of gray levels is measured
within the droplet (figure 4b). This confirms that complete mix-
ing of the two components has occurred, and is set as the time
point t¼ 0 because we assume thatthe mixing is much faster than
the fibrin-forming interactions between protein components. The
evolution of fibrin formation and clotting is shown in figures 4c–
4f, which are taken at increasing distances (and, correspondingly,
different reaction times t) along the device.
The presence of small, high intensity aggregates is found as the
fibrin network develops. The number and size of these aggregates
Fig. 3
(inset, upper left) and fibrinogen (F) solutions form at the T-junctions.
Droplets pair at the Y-intersection and coalesce as they pass through the
electrodes (inset, upper right), and travel through the microchannel
(dimensions given in lower right box).
Serpentine microchip with 4 inlets. Droplets of thrombin (T)
This journal is ª The Royal Society of Chemistry 2009Lab Chip, 2009, 9, 1933–1941 | 1935
Page 4
appear to be inversely related, and eventually a large, single clot
of fibrin is found in droplets at the highest time point, cf. figure
4f. Moreover, the background intensity of the droplet transitions
from light gray, at smallest t, to virtually black, at higher t. For
a first analysis, the dimensionless parameter s*, defined here as
the normalized standard deviation of grayscale intensities in
a droplet, was used to quantify these observations. This
parameter is calculated in the following manner: s* ¼ (s/I)t/(s/
I)t ¼ 0, where I is the mean intensity and s is the standard devi-
ation of the intensities.
The values of s*, averaged over several droplets, are plotted as
a function of time in figure 4. A substantial increase in s* with
increasing reaction time is found. This parameter seems to
accurately describe the aggregation of fibrin as the droplets
proceed through the device. Additionally, values of s* for the
same timepoint (t ¼ 2.7 s) and droplet velocity (v ¼ 5 mm/s) but
with different [F]/[T] ratios 0.5, 1, and 5 are compared in the inset
in figure 4. These ratios are changed by varying the upstream
concentration of thrombin, [T]; in each experiment the concen-
tration of fibrinogen, [F], is kept constant so that the amount of
fluorophore is also conserved. It can be clearly observed that the
aggregation is faster for the smaller ratio [F]/[T] ¼ 0.5, for which
there is an excess of the enzyme thrombin compared to the
substrate fibrinogen. Furthermore, for a higher ratio, [F]/[T] ¼ 5,
the droplets remained homogeneously gray at all points in the
microchip, indicating that the accessible time scale (tmax? 30 s) is
not long enough in this case to visualize fibrin formation. The
evolution of large scale aggregation, and the corresponding
increase in s*, is particularly striking when compared to the
values of s* observed for fibrin networks formed under stopped
flow conditions. Using a microdevice of similar thickness but
wider opening, it was possible to coalesce droplets and then hold
them in a single location, thereby stopping the movement of the
droplet (device not shown). In these stopped flow conditions, s*
does not increase significantly from the starting value of 1, when
the two components have initially homogenously mixed. A good
example of the type of fibrin network formed in stopped flow can
be found in figure 6a. In these conditions, the formation of
a three-dimensional fibrin network results in a slight increase in
s*. However, this value remains very low over all measured
timescales (e.g. 1 hour, results not shown). Most importantly, s*
in stopped flow never approaches the higher values of s*
measured for moving droplets containing large aggregates.
The direct comparison between these two droplet conditions
clearly demonstrates that the flow fields in moving droplets play
an important role in the aggregation of fibrin networks. These
flow fields apparently induce and accelerate fibrin interactions,
culminating in protein aggregation. However, the circulating
flow fields in microdroplets are known to be complicated. Mixing
between two liquids coalesced into a single compartment has
been described as chaotic advection.31Recent measurements
using confocal-PIV to follow the fluid motion in plug-shaped
droplets indicate that indeed the circulating flow patterns are far
from straightforward, with several vortices found at droplet
edges.32,33The flow direction and magnitude depends on the
position within the droplet and is driven by shearing interactions
between the droplet and the microchannel wall. For the type of
adjacent (i.e. axial) mixing scenario used here, two circulation
vortices are seen when viewing the droplet in 2D, at the center of
which are stagnant zones.34For clarification, some streamlines
within a moving droplet are sketched in the inset of figure 5. In
similar plug-shaped droplets, the vortices at fluid-fluid interfaces
can have velocities nearly 25% higher than the bulk droplet
velocity (based on other measurements in our lab).
The complicated flow fields in the droplets directly impact the
fibrin growth in a manner that is not entirely straightforward.
The formation of fibrin protofibrils is an intermediate step in the
fibrin pathway, as illustrated in figure 1. The formation and
lateral growth of these fibrils into larger fibers can, for the most
part, be observed at optical resolution. As we cannot observe the
smaller protofibrils using optical methods, the results presented
here are indicative of larger fiber aggregation. The images taken
Fig. 4
bar represents 60 mm. Right: Normalized standard deviation of droplet intensities s* at different time points in flow compared to a droplet in stopped
flow. Inset graph: For the same evolution time, t ¼ 2.7 s, s* varies with [F]/[T] and no fibrin formation is seen for high [F]/[T] ¼ 5 over the entire device
(denoted with *).
Fibrin formation in droplets ([F]/[T] ¼ 0.5, v ¼ 5 mm/s). Left: Representative images from (a) initial mixing stage to (f) final clotting. The scale
1936 | Lab Chip, 2009, 9, 1933–1941 This journal is ª The Royal Society of Chemistry 2009
Page 5
at multiple timepoints clearly show the aggregation of protein
into small clumps and then further aggregation into a single,
large fibrin ''particle''. This is in stark contrast to the droplet-
spanning network of fibers recorded for stopped flow. Even in
this condition, however, it has been seen that movement of
neighboring protofibrils occurs during fibrin formation –
purportedly due to forces exerted by the newly formed fibrin
network – and this fibril contact induces network formation.25
The hydrodynamic conditions within a moving droplet will
contribute to additional, significant impacts on fibrillization.
Irreversible fibrin aggregation in moving droplets is enhanced by
local flow fields and is driven by the proximity of the small,
mobile, and active fibrils to one another and to larger aggregates.
The flow in the droplets increases particle–particle collisions,
where particles can be fibrinogen, thrombin, fibrin fibrils or even
fibrin aggregates. Thus, the flow field influences nearly all levels
of protein formation and behavior. The localized segregation
between fibrin aggregates and solution seen in figure 4 appears to
be a type of complex coacervation similar to what has been seen
with other proteins.35
In summary, the impact of droplet flow fields on protein
aggregation and clotting is an important consideration. The
hydrodynamic effects within a droplet appear to significantly
influence protein interactions and, therefore, comparisons
between in vitro protein behavior and in vivo behavior must be
carefully evaluated. However, it is plausible that flow fields in
blood vessels may also promote molecular crowding and coac-
ervation of fibrin in blood clots, both in blood flow as well as at
the vessel injury site.
Manipulation of fibrin networks
In order to reduce hydrodynamic influences on fibrin formation
and to enable the online manipulation of fibrin networks,
a second microfluidic chip was employed. The ability to ''park''
a droplet creates an environment for internal droplet processes to
proceed over long time scales.36In this microchip, a reaction
chamber allows the fibrin network to evolve in a stopped flow
condition before it is mechanically manipulated through a series
of microchannel geometries. The droplet velocity is reduced in
this reaction chamber by a substantial increase in the channel
width, as shown in figure 5. The velocity of the droplets in the
chamber is controlled not only by the inflow of liquid by the
syringe pumps at the inlets but also by the withdrawal of
continuous phase at an outlet from the side of the reaction
chamber. Consequently, the droplet velocity is tunable and
coalesced droplets can beheld in the reaction chamber for a given
residence time or ''network ripening time'', tn.
Using this channel design, a ripening time tnon the order of
tens of seconds in the reaction chamber is required to observe the
type of network seen in figure 6a, for [F]/[T] ¼ 2. At this time tn,
we observe an isotropic fibrous network that displays multiple
crossing points of fibrils but does not show any large scale
aggregation behaviors (i.e. those found under the flow conditions
in the microchip described earlier). When the coalesced droplet
sits in the reaction chamber, protofibril and larger fiber forma-
tion are able to proceed without any significant influence of
hydrodynamic effects. Also, the fibers' thickness appears to be
conserved for long observation times (e.g. 1 hour), which
suggests that a steady state has been reached. The final result is
a genuine droplet-spanning fibrin network. In the following
analyses we treat this protein network as quasi-two-dimensional,
due to the high aspect ratio of the droplet width to depth (5:1)
and for simplicity of analysis. Some fluorophores are found at
the droplet-oil interface of coalesced droplets (possibly due to the
surfactant system used here), but the fluorescence intensity at the
Fig. 6
is 40 mm. Negligible structural difference is observed in similar confinements (i.e. b and d, c and e), highlighting the elasticity of the fibrin networks at
slow velocities.
Images of the fibrinnetwork in the same droplet ([F]/[T] ¼ 2, vnarrow? 200 mm/s) at positions a–e, corresponding to the sketch of device. Scale bar
Fig. 5
elements for manipulating the fibrin networks. The velocity V2of the side
channel controls the velocity of single droplets traveling through the
microchannel outlet, V1. Some of the flow fields within a moving droplet
in the microchannel are sketched in the upper inset, although detailed
treatments can be found in the literature cited in the text.
Microchip incorporating a reaction chamber and geometric
This journal is ª The Royal Society of Chemistry 2009Lab Chip, 2009, 9, 1933–1941 | 1937
Page 6
interface does not change over long time periods and therefore
this effect may be disregarded in a first approximation. Addi-
tionally, in every case where the fibrin networks form, some
depletion of the network near the droplet-oil interface is
observed, indicating that there are no specific interactions
between the network and the droplet interface.
The fibrous networks are manipulated as they pass through the
microchannel, which contains several geometric obstacles. The
microchip shown in figure 5 contains narrow regions, which
result in a compression of the droplets, followed by wide regions,
which allow the droplet to regain its original circular shape. By
appropriately adjusting the flow at the side channel of the reac-
tion chamber (V2), the droplets are driven through the final
stages of the microchip at velocities ranging up to 1 mm/s.
The images in figure 6 show one droplet prepared at [F]/[T] ¼ 2
as it passes through the microchip. Due to the very slow flow
speeds achievable using these devices, individual droplets could
be followed by translating the microscope sample stage. There-
fore, direct comparisons of the fibrin network during and after
compression were possible. Comparing the squeezed networks in
figures 6b and 6d, one sees qualitatively similar features. This
finding is also true for further constrictions along the micro-
channel. Centrally located fibers extend along the flow axis and
a depletion region is found between the fibrin network and the
surface of the droplet. The fibrin networks in the wide regions of
figures 6c and 6e, where the droplet shape reforms to a nearly
circular cross-section, show a different fiber arrangement that
approaches the isotropic network of figure 6a. Similar features
can be identified when comparing the circular droplets in 6c and
6e, which indicates a restoration of general network features
throughout the droplet's manipulation in the device. Despite the
existence of some weak plastic deformation, figure 6 clearly
shows that the fibrin networks formed under these conditions are
generally able to compress and extend in an almost reproducible
manner. This indicates a considerable degree of structural
integrity and network elasticity. Remarkably, this conservation
occurs despite the fluid flow that percolates the fibrin network in
the moving droplet.
To appropriately describe the experimental condition of the
droplets, we introduce a rate of deformation 3 ¼ Dv/l. Here, Dv ¼
vnarrow? vwideis the velocity difference of the droplet in the two
microchannel widths and l ¼ 160 mm is the typical length scale of
deformation. To a good approximation, the velocities of the
droplet depend on the width ratio of the deformation induced by
the channels, wnarrow/wwide¼ 80 mm /160 mm ¼ 0.5. This allows 3
to be calculated using only vnarrow, which was found to be
consistently accessible experimentally, especially in cases where
the fast moving droplet could not be tracked over long distances
using the microscope stage. Using these assumptions, the rate of
deformation can be calculated using 3 ¼ vnarrow/320 mm?1. Using
these parameters, the data in figure 7 correspond to droplets
undergoing a rate of deformation 3 ¼ 0.6 s?1.
Points of high intensity in the droplets are correlated to fibril
cross-over in the interconnected fibrin network. An analysis of
these points was conducted in order to quantify the structural
similarities (or differences) between the networks in compressed
and widened regions. Using image analysis software, the intense
network features were identified by a binary algorithm with
a conserved tolerance level. Examples of this process are shown
in figure 7, where the original image frame is shown above the
resulting point distributions for a droplet in both a wide (figure
7a) and narrow (figure 7b) channel. The positions of these
features were used to calculate the distance R of each point from
the droplet center (i.e. center of mass). Histograms of these
distances are plotted in figure 7, for a single droplet passing
through wide and narrow channel regions. For comparison, the
distribution of network positions within the droplet in the reac-
tion chamber, i.e. the native fibrin network, is also shown in
figure 7a.
All of the distributions shown in figure 7a for the circular
droplets in wide regions approximately follow a linear scaling in
R up to a given threshold of around R ¼ 45 mm. Depletion of the
network from the droplet-oil interface is evident from visual
inspection of these images and results in a decrease in the
network point frequencies close to the physical droplet radius
(vertical gray line). These results agree with the expected distri-
bution of points contained within a circular area, except for the
depletion effect. The depletion is exacerbated by the presence of
the interacting protein network. A comparison of the distribu-
tion of fluorescent beads in droplets studied in a similar device
(black curve in figure 7a) highlights the significant depletion that
occurs with fibrin networks. Furthermore, a larger depletion of
the network is measured in the wide regions as compared to the
native structure found in the reaction chamber (arrows, figure
7a). This increased depletion is a consequence of droplet defor-
mation and may also be due to neighboring fiber interactions
driven by crowding effects. It is important to note that after the
droplet initially experiences a deformation, the extent of deple-
tion remains conserved. In fact, all of the distributions from wide
channel regions shown in figure 7a (with the exception of the data
from the droplet in the reaction chamber) overlay remarkably
well. This suggests that the fibrin network recovers completely
after repeated cycles of squeezing, which is qualitatively seen in
the microscopy images.
A similar reproducibility is found when considering the
distributions for the elongated droplets in the narrow channels,
figure 7b. In these regions the droplet assumes a plug of stadium
shape, which is neither a rectangle nor an ellipse, and is described
by a short axis asand long axis al. These two length scales emerge
in the distributions and are labeled with vertical gray lines in
figure 7b. For distances less than as, the distributions of inten-
sities scale linearly until reaching a threshold distance of about
25 mm, and then decrease reflecting depletion from the walls at as
in a manner similar to that found in the circular droplets.
However, the linear scaling in the plugs has a slope that is higher
than that measured in the droplets of figure 7a. This suggests an
increased densification of the network when the droplet is
compressed. The behavior of fibrin at distances between asand al
significantly deviates from measurements of fluorescent beads in
similar plugs (black line in figure 7b). Although the distribution
of beads remains high to distances of nearly 100 mm, the
frequency of point distances in the fibrin network substantially
decreases on the same length scale. However, the extent of
depletion is conserved upon repeated compression of the droplet.
There is no observation of delayed fibrin network recovery, as
evidenced by the fact that the distributions shown in figure 7 do
not vary significantly at similarly shaped device positions. The
impressive elasticity of these fibrin networks echoes the results of
1938 | Lab Chip, 2009, 9, 1933–1941 This journal is ª The Royal Society of Chemistry 2009
Page 7
Wen et al., who reported elastic moduli ranging from 50 Pa to
a maximum of 900 Pa for fibrin clots undergoing stress in a cone-
plate rheometer.15These authors also found the dominant fibrin
deformation to be affine, meaning that the local strain at any
point followed the macroscopic strain of the system. The
recovery of the fibrin networks after repeated compressions
reported here suggests that the network exhibits properties
similar to those reported in rheology experiments – including
undergoing affine deformations.
Coacervation of deformed fibrin networks
At slow velocities and rates of deformation, 3, fibrin networks
centered within the droplet can survive several cycles of
compression. Furthermore, the network under these conditions
is elastically deformable. However, at higher 3, inelastic network
properties may be accessed if the deformation is faster than the
recovery of the network. This is achieved by increasing the
droplet velocity through the microchannel (of the microchip
shown in figure 5). At sufficiently high 3, two distinct phases are
present within the droplet. This is clearly visualized in figure 8c,
which shows a droplet with 3 ¼ 1.125 s?1(vnarrow¼ 360 mm/s).
The fibrin network has densified, concentrating toward the rear
of the droplet with respect to the direction of droplet movement
in the microchannel. For comparison, figure 8a shows an image
in the condition where 3 ¼ 0.5 s?1, in which case the network is
distributed across the entire droplet. Based on observation of
droplets moving at different velocities, the extreme separation
into dense fibrin is found for droplets experiencing a rate of
deformation 3 > 1 s?1.
A comparison of the fibrin network conditions in droplets
traveling at different velocities is plotted in figure 8b for [F]/[T] ¼
2. Images can once again be analyzed using the standard devia-
tion of intensities normalized by the mean intensity. In this case,
it is appropriate to use the relation s0¼ (s/I)narrow/(s/I)chamber,
where (s/I)narrowis the value for a droplet undergoing its first
deformation in the narrow region of the microchannel and (s/
I)chamberis the ''original'' value of the isotropic network state of
0.6 s?1. Network points (lower images) are determined from original data (upper images). Droplet radii and axes are marked with vertical gray lines.
Compared to the round droplet in the reaction chamber prior to any compression (black squares), circular droplets show a slight shift in peak frequency
(arrows). The first, second, and third repetitions through the microchip are plotted with circles, triangles, and diamonds, respectively. For comparison,
the histograms for beads in aqueous solution in a similar device are plotted in solid lines for both circles and plugs.
Histogramsof networkpoint distancesfromcenter of massof (a) circularor (b) compressed dropletswith [F]/[T] ¼ 2 andrate of deformation3 ¼
Fig. 8
which is reflected by their higher values of s0(black data points in panel b, also see panel c). No separation is visually observed for 3 less than one, where
s0< 2 (white data points in panel b, also see panel a). The flow fields within droplets in the two conditions are also sketched (below the images in panels
a and b), where the network, drawn in gray, either extends along the entire droplet (a) or resides in the back half of the droplet (b). For comparison, the
horizontal gray line is the average s* value in stopped flow from figure 4. Dotted line is guide to the eye.
Two ''phases'' of fibrin-rich and fibrin-poor regions are found for droplets experiencing rates of deformation 3 approximately one or greater,
This journal is ª The Royal Society of Chemistry 2009Lab Chip, 2009, 9, 1933–1941 | 1939
Page 8
the same droplet while it resided in the reaction chamber.
Comparing the calculated values of s0with visual inspection of
fluorescence images, it appears that s0> 2 correlates with the
segregation of fibrin-rich and fibrin-poor regions within a single
droplet. Moreover, a critical rate of deformation 3 z 1 s?1can be
identified as a threshold for this coacervation behavior.
This behavior can be interpreted as a shape transition in fibrin
networks owing to hydrodynamic flow within a moving and
deformed droplet. As long as the liquid (buffer) flows slowly
through the fibrin network, a small pressure gradient is needed to
accomplish flow and thus the network remains unaffected, aside
from a small elastic perturbation. This corresponds roughly to
the situation sketched in figure 8a. As the flow becomes stronger,
the pressure gradient along the protein network may become
large enough to overcome the elastic forces maintaining its
shape. As it is compressed, the fiber network inside becomes
denser, and the flow resistance increases further. This may lead to
a runaway instability, which finally results in a situation which is
sketched in figure 8c. The flow is now almost entirely expelled
from the protein network.
In order to gain some quantitative understanding of this effect,
we start by assuming the network forms at some initial axial
length l0, which is given, e.g., by the length of the water droplet.
As the flow increases, this length may change and will be called l.
Weintroduce the dimensionless quantity x ¼ l/l0for convenience.
The force (per area) that is needed to elongate or compress the
network longitudinally is Fl¼ E(x ? 1) given by Hooke's law (E
is Young's modulus). The flow rate within the fiber network is
given by VpP/h, where Vp is the pressure gradient, h is the
viscosity of the liquid, and P is the permeability of the network.
Since the permeability of a mesh is roughly (up to a prefactor of
order unity) given by the square of the mesh width, we can obtain
an expression for P as a function of the network density. If d0is
the average diameter of the fibers, we find
where r0< 1 is the initial density of the network directly after
formation. The force (per area) exerted onto the network
longitudinally owing to the hydrodynamic flow is
where_V is the flow rate, which is related to the deformation rate
by_V ¼ 3a3(a is the radius of the droplet). The network's ''bulk''
shape transition takes place where Fl? Ffhas a degenerate zero.
We define a dimensionless scales deformation rate
~ 3 ¼
which is of order unity at the transition. This corresponds to
a Young's modulus of the fibrin network within a plug in an
elastic moduli range that was reported by Wen et al.15Therefore,
we find that this simple physical model is both compatible with
existing descriptions of fibrin networks and is able to explain our
new experimental evidence of a transition at a critical rate of
deformation 3 z 1 s?1.
The effect of this threshold deformation rate is manifested as
irreversible clotting into a dense fibrin network. In the reaction
chamber, the droplets initially contained an isotropic, fibrous
ripened network. This is considerably different to the homoge-
nous mixture used as the starting point in measurements of s* in
the serpentine device, where the continuously moving droplet did
not allow droplet spanning network formation. The fact that
a similar s parameter describes the aggregation phenomena in
both cases demonstrates the generality of hydrodynamically
induced aggregation. Therefore, these hydrodynamic effects may
be a crucial consideration in droplet-based experiments, where
multiple components experience microfluidic flow conditions.
This effect is especially important in bionetwork formation, as
shown here, and other processes such as polymerization (e.g.
online particle or capsule synthesis). Furthermore, the complex
effects of hydrodynamics on network aggregation under micro-
fluidic flow conditions might suggest a general tendency of fibrin
networks to aggregate in vitro. The preferred aggregation states
also serve as a reminder that the networks are delicate and non-
equilibrium in their nature and therefore access to them, via
microfluidic tools, is particularly novel.
The protein fibrin was selected to explore the influence of
microfluidic flow on the formation and aggregation of a bionet-
work. By its nature as a primary component of blood clots, fibrin
exhibits strong adhesion to surfaces including microchannel
walls. Therefore, the networks in this study were confined within
droplets. This was achieved using tailored microfluidic chips,
containing sites for droplet formation, electrocoalescence, in situ
observation, andmechanical
networks. The formation of fibrin was initiated in a droplet by
coalescing two droplets, one with the fibrinogen monomer and
the other containing the enzyme thrombin. The development of
fibrin fibers within the resulting droplet required time for acti-
vation and fibril growth, and eventually neighboring fibers
interacted to form a three-dimensional network.
Hydrodynamic flow within the droplets was found to
dramatically accelerate the aggregation of fibrin into small and,
eventually, very large particles, i.e. clots. However, in stopped
flow environments, isotropic three-dimensional networks were
produced. In this case, the fibrin formation was not influenced by
extreme flow patterns because it remained ''parked'' in
a chamber. These isotropic networks were then driven through
repeated geometric confinements to study the elasticity of the
networks. Fluorescence analysis of the fibrin network at slow
velocities did not show any evidence of inelastic deformation,
despite undergoing repeated cycles of compression. However,
a critical rate of deformation 3 was identified, above which fibrin-
rich and fibrin-poor regions appear within the droplet. In this
case, the clotting behavior of fibrin into a dense pellet within the
droplet occurs as a result of surpassing a critical hydrodynamic
force on the network. In both microchips, the standard deviation
of intensities normalized by the mean intensity, i.e. s* or s0, is an
appropriate parameter to quantify the extent of aggregation.
manipulation of the fibrin
1940 | Lab Chip, 2009, 9, 1933–1941This journal is ª The Royal Society of Chemistry 2009
Page 9
Our microfluidic approach allows the visualization of fibrin
coacervation under a variety of experimental conditions.
Therefore, the tendency of fibrin networks to aggregate can be
approached in multiple ways to understand some general prin-
ciples of the protein's behavior. In the case of fibrin, its naturally
''sticky'' properties are conserved in the microchips, which
manifests as a form of ''clotting''. High quality fluorescence
images allow the direct visualization of the networks and
aggregates. This, in concert with precise mixing of small volumes
in microfluidic devices, enables detailed studies of network
behavior and conformation under confinement and well-
controlled experimental conditions. Generally speaking, the
powerful experimental approach demonstrated here is broadly
relevant to a wide variety of physical systems where a greater
understanding of the delicate interplay between material prop-
erties and flow is desired.
The authors thank Udo Krafft for technical assistance and
Audrey Steinberger for sharing her preliminary experimental
data on droplet microflow environments. H.E. acknowledges
a fellowship from the Alexander von Humboldt foundation.
Funding was provided by the Deutsche Forschungsgemeinschaft
in the framework of SPP 1164 ''Micro- and Nanofluidics'' (PF
375/4, SE 1118/2, SE 1118/4) and SFB 755 ''Nanoscale Photonic
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text:
Posloszny wins Bednarik
ORLANDO, Fla. -- Penn State linebacker Paul Posluszny won the Chuck Bednarik Trophy on Thursday night, given to the best defensive player in the country.
The other finalists were Ohio State linebacker A.J. Hawk and Maryland linebackers D'Qwell Jackson. Posluszny led a resurgence at Penn State. The Nittany Lions (10-1) won the Big Ten and will play in the Orange Bowl after winning just seven games the previous two seasons. Posluszny ranks fourth in the Big Ten with 111 tackles and an average of 10.1 tackles per game. He has 11 tackles for a loss and three sacks. He is just the fourth player in school history to record more than 100 tackles in consecutive seasons. Georgia defensive end David Pollack won the award last season. link-----> http://www.latimes.com/sports/colleg...gefb-headlines |
Re: Posloszny wins Bednarik
Congrats Paul!
Re: Posloszny wins Bednarik
Linebacker U strikes again !!! Woo Hoo !!
Re: Posloszny wins Bednarik
The Linebacker U Attack is HERE TO STAY AT PENN STATE!!!!!
Re: Posloszny wins Bednarik
Poz wins Butkus!!!
ORLANDO, Fla. -- Penn State's Paul Posluszny, who helped the No. 3 Nittany Lions earn a share of the Big Ten championship, won the Butkus Award as the nation's best linebacker on Saturday night. The award, given by the Orlando Downtown Athletic Club, is Posluszny's second national honor. He won the Bednarik Award as the nation's best defensive player on Thursday. "They're both huge honors, but I'd have to say, as a linebacker, that this one means a lot more to me," Posluszny said. "Playing linebacker, to win the Butkus Award means you're the top person at your position and that's the biggest thing you can do." Posluszny beat out Ohio State's A.J. Hawk and Alabama's DeMeco Ryans in becoming the second Penn State linebacker to win the Butkus Award in its 21-year history. LaVar Arrington won in 1999. This season, Posluszny has 111 tackles, including 11 for loss, and three sacks. link-----> http://sports.espn.go.com/ncf/news/story?id=2255300 |
Re: Posloszny wins Bednarik
damn i have no idea who this dude is but he seems good, is this dude a seinor??? and will he get drafted high?
Re: Posloszny wins Bednarik
http://img.photobucket.com/albums/v3...ate/292523.jpg |
Re: Posloszny wins Bednarik
Awesome job! Congrats to him!
Re: Posloszny wins Bednarik
Re: Posloszny wins Bednarik
Here are some quotes on Poz from former Penn State, and Steeler great Jack Ham...
"I truly believe," Jack Ham was saying the other day, "he's the best linebacker ever to play at Penn State." "It's such a different game now than when we played," Ham said. "Today, you have to be half-strong safety, half-linebacker to play. We weren't asked to cover the way these guys are. They didn't stretch the field on us. There were no three- and four-wide receiver sets. A lot of linebackers have to go to the bench in passing situations now. Not Posluszny. He does it all." "I can't think of a linebacker here who played the run as well as he does," Ham said. "Shane Conlan, maybe ... "Watch him. He never gets knocked off his feet. He plays off blocks so well. He never misses tackles." "I've always thought [Dennis] Onkotz was the best linebacker in pass coverage here," Ham said. "This kid might be better. He understands the passing game so well." "I don't know how fast [Posluszny] is in the 40, but I'll bet you'd be amazed if you timed him for 10 yards," Ham said. "He has that burst to the football." "He shouldn't leave early," Ham said. "He should take a page out of A.J. Hawk's book and stay for another year." "There's too much of an upside for [Posluszny] to stay," Ham said. "He would get so much stronger, number one. He would become that much better. He would only enhance his draft status. I don't know where he'd be picked if he came out now, but he'll be a top-10 pick the next year." "The best ever here," Ham said, knowingly. "No doubt about it." |
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subset: commoncrawl


text:
Ubuntu Security Notice (C) 2007-2013 Canonical, Inc. / NASL script (C) 2007-2013 Tenable Network Security, Inc.
Synopsis :
The remote Ubuntu host is missing a security-related patch.
Description :
USN-453-1 provided an updated libx11 package to fix a security
vulnerability. This triggered an error in rdesktop so that it crashed
on startup. This update fixes the problem.
Solution :
Update the affected rdesktop package.
Risk factor :


text:
Consider These Important Aspects Of Web Design
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Getting into web design is something that is going to open a lot of doors for you in the future, especially with the way the digital world is expanding and being integrated into our lives. If you want to learn about web design, then read through this article and see how you can get into it and feel confident in the subject.
When you're thinking about how to design a website, you need to be sure to think about the navigation. You want your navigation to be easily accessible and easy to use. Put the navigation bar on every page in a noticeable place. Also, make sure that it flows well with the rest of your page and doesn't distract visitors.
Don't try to fit too much onto one page when you're designing a website. If your page is too busy it will take a lot longer to load and can overwhelm visitors. When you're going to be putting up a lot of content, create pages for everything you can to reduce the clutter on your page.
Although it is common to see the www. at the front of a website URL, you should try to make sure that you can access your site whether you choose to include it or not. This will make it much easier for anyone to access regardless of how they type it.
Learn web design shortcuts and make good use of them. There are often shortcuts that can be used for just about anything when it comes to web design. For example, you can use certain HTML codes to make very quick changes without needing to re-load.
Now that you've learned some of the ins and outs of web design, you should, hopefully, be a bit more eager to use it to your advantage and gain a reasonable amount of profit through it. Web design is the future and now you have a good idea of how to become good at it. Use this to your advantage and become successful for years to come.
Advertising On The Internet With A Shoestring Budget
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Advertising On The Internet With A Shoestring Budget
How Do You Manifest Your Full Potential For Advertising Online?
By far, the best way to market online for free is through social media outlets. There has never been a greater way to spread your marketing skills than through online media. Essentially, sites like Facebook and Twitter are free to use. Additionally, there are millions of users worldwide. Therefore, you can make good use of the free network and millions of users by promoting and advertising strategically.Check out this link Read more
Beyond Social Networking: How to Network Using Other Methods
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Beyond Social Networking: How To Network Using Other Methods
A Wider Look At Social Media
Social media has dominated the market for networking and marketing. In fact, it is the world's leader in connecting communication and worldwide access. Social media reaches the largest possible audience in the shortest amount of time. This is a hard statistic to compete with. However, other methods of networking exist outside the web of social media.
Alternatives To Social Media Networking
What are some alternatives to social media networking? You can still network through print Read more
Blogging To Increase Your Internet Presence
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Blogging is a great way to get your name and brand out there. Blogging requires that you either have a site or webpage that you can actually add entries to. There are many blogging software plugins that you can utilize so that you can easily add blogs from either a laptop, tablet or even your phone. The way that blogging increases your Internet presence is simply because you will be more likely to attract visitors to your site. One example of this is if you blog about something in particular and someone does an Internet search for that thing.Get Read more
Social Networking And Your Personal Image
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Social networking has revolutionized the way people interact and connect with each other. Through the social media networks, you can share your story with friends, fans and followers. To many, this is appealing as the interaction is two ways. When you post on the wall to update your status, you will receive immediate feedback or comments from the viewers. This is the most attractive part of being active on a social network.
However, if you do not tread carefully, social networking can also reveal its downside: your posts are Read more
Making Sure Your Content Is Not Plagiarized
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Today, many writers use external sources, to help them back up their own written work. But, before you submit a piece of written work as being your own product, you must ensure that you are properly citing the sources you use, and are giving credit where credit is due. You cannot use another author's work without citing to it, and saying that you used an external source. You must cite to the other pieces of work you used, before you use it. Whether you use a book, or an online site, for additional information and credibility to your own work, Read more
How to Build Your Online Brand
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The Internet is an important tool for modern businesses. From the growing amount of people logging on everyday, to the new advances that exist in website design, there are many ways to go about gaining exposure through the various methods available online. In order to successfully build an online brand, there are a couple important elements to consider that can help make the entire process is easy and effective.
Good Website Design
Good website design is an extremely important element in building a successful online brand. Read more
Thinking Outside the Box: New Uses for Social Networking
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When social networking sites originally started, they were mostly used for celebrities and businesses as a way to get information to fans and clients. Now people are finding more creative uses for social networking sites and every day there is a new idea.
A social networking site provides a person with instant access to hundreds of people, so any kind of message can be sent out to all of these people at once using a site Read more
Trends We're Seeing in Web Design
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Whether you're marketing TV Direct to the consumer or selling shoes online you've got to have the basics down when you're working on web design. Here are a few of the trends we keep seeing in the online world and what you can do with them…
Negative Space – it's back. Try incorporating some white space and lots of "dead" page in your design – it will make whatever else you put on the page stand out even more.
Serif – Designers are finally Read more
How to Build Your Webpage Using a Template
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Designing a website from the ground up can be quite the task. Whether you are doing it from a blank notepad page, or loading up your potential website in Dreamweaver, or Frontpage, there are templates for every style you want. In the older days of design, a template was just a skeleton, now they come complete with graphics, and easy to follow instructions. All perfectly laid out to look professional, creative, and allow you to dive right in and start adding your own content.
The first thing you need to Read more
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Winland Electronics Announces Receipt Of Stock Exchange Compliance Notice
Winland Electronics, Inc. (NYSE Amex: WEX) ("Winland") announced that it received a notice from NYSE Amex LLC (the "Exchange") indicating that Winland is not in compliance with certain of the Exchange's continued listing standards as set forth in Part 10 of the Exchange's Company Guide (the "Company Guide"), and Winland has therefore become subject to the procedures and requirements of Section 1009 of the Company Guide. Specifically, Winland was cited by the Exchange for noncompliance with the following section of the Company Guide:
- Section 1003(a)(iii) – stockholder's equity of less than $6,000,000 and losses from continuing operations and/or net losses in Winland's five most recent fiscal years.
Winland has been afforded the opportunity to submit a plan of compliance to the Exchange by May 11, 2012 that provides for Winland to regain compliance with Section 1003(a)(iii) by May 29, 2013. If Winland does not submit a plan or if the plan is not accepted by the Exchange, Winland will be subject to delisting procedures as set forth in Section 1010 and part 12 of the Company Guide.
About Winland Electronics
Winland Electronics, Inc. ( www.winland.com) is an industry leader of critical condition monitoring devices. Products including EnviroAlert, WaterBug, TempAlert, Vehicle Alert and more are designed in-house to monitor critical conditions for industries including health/medical, grocery/food service, commercial/industrial, as well as agriculture and residential. Proudly made in the USA, Winland products are compatible with any hard wire or wireless alarm system and are available through distribution worldwide. Headquartered in Mankato, MN, Winland trades on the NYSE Amex Exchange under the symbol WEX.
Cautionary Statements Certain statements contained in this press release and other written and oral statements made from time to time by Winland do not relate strictly to historical or current facts. As such, they are considered forward-looking statements, which provide current expectations or forecasts of future events. The statements included in this release with respect to meeting the Exchange's continued listing standards by May 29, 2013 and that no other events will jeopardize Winland's continued listing on the Exchange are forward-looking. No forward-looking statement can be guaranteed and actual results may vary materially.Check Out Our Best Services for Investors
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Topics :: politicians
1 thru 10 of 21 Stories
GOP Congressional Candidate Features Gay Son in Ad
Nan Hayworth, the Republican seeking to unseat out Rep. Sean Patrick Maloney in New York's 18th Congressional District, released a television ad Wednesday featuring her gay son.
2016 Campaign Checklist: They've All Been So Busy
A look at the politicians who may run for president in 2016.
Chuck Hagel Confirmed as Defense Secretary
After weeks of delay, the U.S. Senate today confirmed Chuck Hagel as the next secretary of defense, voting 58-41.
Ed Koch, Mayor Who Became a Symbol of NYC, Dies
Ed Koch, former mayor of New York City and champion of gay rights, died Friday from congestive heart failure at the age of 88.
Barney Frank Wants to be Interim Mass. Senator
Although Barney Frank has only been out of Congress for a single day, he said he told Massachusetts Gov. Deval Patrick that he wants to be interim senator when Sen. John Kerry leaves to become secretary of state.
Brian Sims Win as PA's First Out Representative Indicative of National Move Toward LGBT Inclusiveness
The recent election of Brian Sims as Pennsylvania's first out-gay representative is another example of the national sea change of LGBTs becoming involved in politics at all levels.
New Faces: Newly Elected US Senators
Here is a look at the newly elected U.S. senators from Tuesday's election.
Clothing for the 47%
Looking for clothing for the 47%? The Mitt Zombie tee lets everyone know where you stand in this fall's election. Wear this tee shirt proudly and help entitle your fellow Americans to some good old fashioned political humor.
Barbs Traded by Candidates in Sacramento Council Race
Two gay candidates running for a Sacramento City Council seat are trading barbs on the campaign trail ahead of the June vote.
SF Dem Candidates Differ on Party Panel Makeup
Once again control of the local Democratic Party in San Francisco is up for grabs this June.
1 thru 10 of 21 Stories


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7 students allegedly caught with alcohol at Powell Middle School
The mother of a Powell Middle School eighth-grader said she is frustrated by the conflicting information from school officials about an incident surrounding a student bringing alcohol to school that involved her daughter — including a possible punishment.
On Friday, school officials found alcohol among seven students who were in the seventh and eighth grade shortly before school began, Melissa Ogden, schools spokeswoman confirmed on Wednesday.
One of the students, she said, was taken to the hospital by their parents.
Ogden said "appropriate disciplinary action was taken," but she would not share specifics, citing the Family Educational Rights and Privacy Act.
According to the school system's policy, if a student is found to have alcohol at school they "shall be subject to suspension."
Ogden said per the policy, school officials also contacted the Knox County Sheriff's Office about the incident, but "a police report was not filed and there is no investigation."
Laura Smith, whose daughter was among the seven students, said Wednesday that she didn't find out about the incident until about 12:15 p.m. Friday, when she got a call from the school saying her daughter had been suspended. Smith says she then got a later call about 4 p.m. saying that her daughter's suspension had been lifted.
"(My daughter) went to school Monday thinking that everything was fine, only to be suspended again (Tuesday)," Smith said. "They said they had new evidence, but we're at the point now where it's he said-she said story and there is no evidence. I'm just disappointed in the way that it was handled."
Smith said school officials told her Friday that her daughter had held a water bottle that contained oxycodone-laced alcohol in her hand and had smelled it, but did not drink it. Smith said she was later told by school officials that her daughter had drank liquid.
"My daughter is very adamant that she did not," she said. "There was supposed to be a video camera that could see it but then they're telling me that it was too grainy and I'm thinking if the video camera is there for student's protection it should actually work."
Smith said a disciplinary hearing has been scheduled for her daughter for Thursday afternoon, but she has no idea what the results may be.
If her daughter is suspended the penalty range could be anywhere from five to 180 days.
"What's more upsetting is they waited until (Tuesday) to try and take care of this and now it's going to basically ruin the first year of my daughter's high school career if she gets expelled," Smith said. "She's never been in trouble before. I think that's why we've been so floored by it all."
Follow Lydia X. McCoy's tweets on education at www.twitter.com/lydiaXmccoy.
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Part Number WB23X10005 (AP2023893) replaces 769678, AH236430, EA236430, PS236430.
Thermal Limiter 230


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Article here
Gunshot kills Indy man, 21
By Vic Ryckaert
Indianapolis homicide detectives are investigating the death of a 21-year-old man who died at the hospital after suffering a gunshot wound to the leg.
The victim was shot in the right knee at a home in the 300 block of North Temple Avenue about 12:30 a.m. this morning, police said. He was pronounced dead at Wishard Memorial Hospital.
The victim's name is being withheld pending notification of his family.
What was he hit with...an RPG???


text: also sprach "J.A. Neitzel": > > Sir Belford didn't tell us he used "inetd just for fun". I guess we > assumed too much. I wonder... Sir Belford replies and thanks Lord Neitzel for his kind appellation - as do the gentlemen of court, my cats, Master Badger and Mister Bigglesworth. No I don't run "inetd just for fun" - or anything else I can avoid. Whether that is due to sheer laziness or the appeal of minimalism remains moot. It really, truly is a home PC; I use a modem to connect the nasty outside world; don't run any ftp, http servers - in any event, I've nothing to offer the outside world by way of interesting files or whatever. My main purpose in building LFS is: 1) to learn somewhat about Linux; 2)to avoid the bloated OS's I would otherwise be lumbered with. (I do run Win 98 - for a printer, a scanner, and the best game ever written, Sid Meier's Civilization). I'm rambling. I've nothing on this sytem that desparately needs protection, but security seems an interesting field of enquiry - hence my pursuit of it. Alternatively, I employ the streaker's defence: "it seemed, Your Honour, like a good idea at the time". -- Fergus Belford fbmail at ozemail.com.au -- This day shall not come again, Each minute a priceless gem. -- Unsubscribe: send email to listar at linuxfromscratch.org and put 'unsubscribe blfs-support' in the subject header of the message


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Relm Communications, Incorporated, dba BK Radio, Incorporated, was awarded on August 26, 1996, a firm fixed price contract with an estimated not-to-exceed cumulative total of $40,500,000 (appropriation number and dollar value will be issued with each delivery order) for indefinite delivery 5-year requirements acquisition for the AN/PRC-127(A) radio set including 1st year requirements for six replacement parts. Work will be performed in West Melbourne, Fla., and is expected to be completed by March 31, 2002. Bids were solicited on the electronic bulletin board on July 1, 1996, and two bids were received. The contracting activity is the U.S. Army Communications and Electronics Command, Ft. Monmouth, N.J. (DAAB07-96-D-C015).
Geo-Centers Incorporated, Newton Centre, Mass., is being awarded a $5,878,509 cost-plus-fixed-fee contract for acquisition of research and development of material for naval weapons. This contract contains options which, if exercised, will bring the cumulative value of this contract to $24,560,769. Work will be performed in Washington, D.C. (70%), and Newton Centre, Mass. (30%), and is expected to be completed by August 1997. Contract funds in the amount of $460,000 will expire at the end of the current fiscal year. This contract was competitively procured with 48 proposals solicited and one offer received. The Naval Research Laboratory, Washington, D.C., is the contracting activity (N00014-96-C-2097).
Harper/Nielsen Dillingham Builders, Incorporated, San Diego, Calif., was awarded on August 26, 1996, a $17,724,714 firm fixed price contract to provide for construction of 143 units of military family housing at Vandenberg Air Force Base, Calif. The work will be performed at Vandenberg Air Force Base, Calif. Contract is expected to be completed January 1998. Contract funds will not expire at the end of the current fiscal year. There were 36 firms solicited and three proposals received. Solicitation began June 1996; negotiations were completed July 1996. The 30th Space Wing, Vandenberg Air Force Base, Calif., is the contracting activity (F04684-96/C-0046).


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LIKE the disco era it dominated, stagflation has a distinctive beat: slow growth, rising inflation, high oil prices and weak labour markets. In the 1970s this nasty combination haunted the global economy. Could it be making a comeback?
Today's world economy does seem to be playing some similar tunes. In the statement accompanying its latest interest-rate hike on May 3rd, America's Federal Reserve fretted about both price pressure and a slowdown in spending. On May 4th, the European Central Bank kept interest rates unchanged, but worried aloud about oil prices and slowing growth.
The evidence is mounting that global growth has slowed. In America, output grew by an annualised 3.1% in the first three months of 2005, the slowest pace for two years. More recent figures, from weak retail sales to soggy consumer confidence, suggest this "soft patch" may be getting softer by the day. In Britain, the latest numbers—in retail sales and manufacturing—point to weaker growth. And in the euro zone, sluggish economies are looking ever more lethargic.
Yet even as growth is slowing, price pressures are looming. In America, consumer prices rose 3.1% in the year to March, up from 1.7% a year ago. In Britain, inflation jumped unexpectedly in March. And in the euro zone, consumer prices are still rising faster than the 2% goal that the European Central Bank targets. With output slowing and inflation stubborn, it is small wonder that the concerns about stagflation are back in fashion.
In fact, today's version of stagflation bears scant resemblance to the 1970s. In 1979, for instance, America's core inflation, which excludes oil and food, was rising at over 7% a year, while the economy grew barely more than 1%. Recent core inflation, at 2.2%, is only just above the central bank's comfort zone, while GDP growth is pretty close to the economy's sustainable rate. There is a tad of "flation", in other words, but not much sign of "stag". The euro zone, by contrast, has plenty of stagnation, but—despite the ECB's nervousness—there is little sign that its inflation is getting out of control (see article).
Just because things are not as bad as the 1970s does not, by itself, give much cause for comfort, however. How far history repeats itself hinges on two other factors. The first is central bankers' determination to retain their credibility as inflation fighters. The 1970s stagflation resulted, in large part, from extended periods of loose monetary policy pursued to accommodate the demand-crippling effect of oil shocks by printing money. The credibility-obsessed folk at the ECB clearly have no intention of repeating that mistake.
But the Fed's governors have played a riskier game. They have, thus far, run an extremely loose monetary policy—even after this week's rise, real interest rates are barely positive. But thanks to the central bank's reserve of inflation-fighting credibility, long-term inflation expectations have barely shifted. At issue is how long that remains the case. At the very least, the measured march to higher rates must continue unabated.
The other wild card combines labour costs and productivity growth. In the 1970s, productivity growth fell sharply and unexpectedly. Added to this, strong trade unions, little international competition and those accommodating central bankers created a pernicious wage-price spiral. There is little of this dynamic today. Although productivity growth has slowed from its recent peaks, it has not slumped. Global competition has left little room for excessive wage demands. This suggests that a return to classic stagflation is unlikely.
Stayin' alive
But the modern remix still poses problems. Steering monetary policy when growth is slowing and prices are accelerating is never easy. It is particularly hard in today's unbalanced world economy, where too much depends on continued spending by American consumers who, in turn, are counting on an unsustainably frothy housing market. At some point, America's heavily indebted consumers will need to cut back spending. And when that happens, those in the rest of the world will have to start spending more to keep the world economy growing. The real risk is that Washington's central bankers will be too worried about stagnation and Frankfurt's too worried about inflation to allow that to happen.


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Sarah Palin escapes flying tomato attack
(Read article summary)Sarah Palin dodged flying tomatoes yesterday in Bloomington, Minnesota
Jake Turcotte
It's December. Time for holiday traditions.
Most of us engage in the standard holiday fare. Putting up Christmas trees. Lighting the Menorah. Some have a more unconventional approach. The gang in the sitcom "It's Always Sunny in Philadelphia," for example, celebrates by throwing rocks at trains.
Maybe that's where the idea came from….
For the second year in a row, December has been the month where people throw things at politicians.
You remember last December when President Bush was the victim of a flying shoe attack? This time, former vice presidential nominee Sarah Palin was the target. The weapon of choice? Tomatoes.
Much like Bush, Palin was unscathed in the attack. As you recall, Bush escaped because of his ninja-like dodging moves. Palin avoided disaster because the assailant was a bad shot. A really bad shot.
Tomatoes Going Rogue
All the drama occurred yesterday at the Mall of America in Bloomington, Minnesota. Palin was at another stop on her "Going Rogue" book tour.


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Reviews, reviews, reviews...
FreakScore is a weighted average of all aggregated professional and user review scores. Read more
This product has a FreakScore of 5.2* out of 10 based on 2 scores.
*Score is uncertain and deviates toward category average due to low number of scores.
The GZ-MC500 creates sharp, vivid and pristine images by dedicat Read more
Best Price at Amazon


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From Wikipedia, the free encyclopedia - View original article
This article needs additional citations for verification. (September 2007) |
Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. It was invented by Alexander Graham Bell.
In balanced pair operation, the two wires carry equal and opposite signals and the destination detects the difference between the two. This is known as differential mode transmission. Noise sources introduce signals into the wires by coupling of electric or magnetic fields and tend to couple to both wires equally. The noise thus produces a common-mode signal which is canceled at the receiver when the difference signal is taken.
This method starts to fail when the noise source is close to the signal wires; the closer wire will couple with the noise more strongly and the common-mode rejection of the receiver will fail to eliminate it. This problem is especially apparent in telecommunication cables where pairs in the same cable lie next to each other for many miles. One pair can induce crosstalk in another and it is additive along the length of the cable. Twisting the pairs counters this effect as on each half twist the wire nearest to the noise-source is exchanged.
Providing the interfering source remains uniform, or nearly so, over the distance of a single twist, the induced noise will remain common-mode. Differential signaling also reduces electromagnetic radiation from the cable, along with the associated attenuation allowing for greater distance between exchanges.
The twist rate (also called pitch of the twist, usually defined in twists per meter) makes up part of the specification for a given type of cable. Where nearby pairs have equal twist rates, the same conductors of the different pairs may repeatedly lie next to each other, partially undoing the benefits of differential mode. For this reason it is commonly specified that, at least for cables containing small numbers of pairs, the twist rates must differ.[1]
In contrast to ScTP (screened twisted pair), STP (shielded twisted pair), FTP (foiled twisted pair) and other shielded cabling variations, UTP (unshielded twisted pair) cable is not surrounded by any shielding. It is the primary wire type for telephone usage and is very common for computer networking, especially as patch cables or temporary network connections due to the high flexibility of the cables.
The earliest telephones used telegraph lines, or open-wire single-wire earth return circuits. In the 1880s electric trams were installed in many cities, which induced noise into these circuits. Lawsuits being unavailing, the telephone companies converted to balanced circuits, which had the incidental benefit of reducing attenuation, hence increasing range.
As electrical power distribution became more commonplace, this measure proved inadequate. Two wires, strung on either side of cross bars on utility poles, shared the route with electrical power lines. Within a few years, the growing use of electricity again brought an increase of interference, so engineers devised a method called wire transposition, to cancel out the interference.
In wire transposition, the wires exchange position once every several poles. In this way, the two wires would receive similar EMI from power lines. This represented an early implementation of twisting, with a twist rate of about four twists per kilometre, or six per mile. Such open-wire balanced lines with periodic transpositions still survive today in some rural areas.
Twisted pair cables were invented by Alexander Graham Bell in 1881.[2] By 1900, the entire American telephone line network was either twisted pair or open wire with transposition to guard against interference. Today, most of the millions of kilometres of twisted pairs in the world are outdoor landlines, owned by telephone companies, used for voice service, and only handled or even seen by telephone workers.
UTP cables are found in many Ethernet networks and telephone systems. For indoor telephone applications, UTP is often grouped into sets of 25 pairs according to a standard 25-pair color code originally developed by AT&T Corporation. A typical subset of these colors (white/blue, blue/white, white/orange, orange/white) shows up in most UTP cables. The cables are typically made with copper wires measured at 22 or 24 American Wire Gauge (AWG),[3] with the colored insulation typically made from an insulator such as polyethylene or FEP and the total package covered in a polyethylene jacket.
For urban outdoor telephone cables containing hundreds or thousands of pairs, the cable is divided into smaller but identical bundles. Each bundle consists of twisted pairs that have different twist rates. The bundles are in turn twisted together to make up the cable. Pairs having the same twist rate within the cable can still experience some degree of crosstalk. Wire pairs are selected carefully to minimize crosstalk within a large cable.
UTP cable is also the most common cable used in computer networking. Modern Ethernet, the most common data networking standard, can use UTP cables. Twisted pair cabling is often used in data networks for short and medium length connections because of its relatively lower costs compared to optical fiber and coaxial cable.
UTP is also finding increasing use in video applications, primarily in security cameras. Many cameras include a UTP output with screw terminals; UTP cable bandwidth has improved to match the baseband of television signals. As UTP is a balanced transmission line, a balun is needed to connect to unbalanced equipment, for example any using BNC connectors and designed for coaxial cable.
Twisted pair cables are often shielded in an attempt to prevent electromagnetic interference. Shielding provides an electric conductive barrier to attenuate electromagnetic waves external to the shield and provides conduction path by which induced currents can be circulated and returned to the source, via ground reference connection.
This shielding can be applied to individual pairs or quads, or to the collection of pairs. Individual pairs are foiled, while overall cable may use braided screen, foil, or braiding with foil.
ISO/IEC 11801:2002 (Annex E) attempts to internationally standardise the various designations for shielded cables by using combinations of three letters - U for unshielded, S for braided shielding, and F for foiled shielding - to explicitly indicate the type of screen for overall cable protection and for individual pairs or quads, using a two-part abbreviation in the form of xx/xTP.
When shielding is applied to the collection of pairs, this is usually referred to as screening, however different vendors and authors use different terminology, employing "screening" and "shielding" interchangeably; for example, STP (shielded twisted pair) or ScTP (screened twisted pair) has been used to denote U/FTP, S/UTP, F/UTP, SF/UTP and S/FTP construction.[4]
Because the shielding is made of metal, it may also serve as a ground. Usually a shielded or a screened twisted pair cable has a special grounding wire added called a drain wire which is electrically connected to the shield or screen. The drain wire simplifies connection to ground at the connectors.
An early example of shielded twisted-pair is IBM STP-A, which was a two-pair 150 ohm S/FTP cable defined in 1985 by the IBM Cabling System specifications, and used with token ring or FDDI networks.[4][5]
Common shielded cable types used by Cat. 6a, Cat.7 and Cat.8 cables include:
Industry acronyms | ISO/IEC 11801 name | Cable screening | Pair shielding |
UTP | U/UTP | none | none |
STP, ScTP, PiMF | U/FTP | none | foil |
FTP, STP, ScTP | F/UTP | foil | none |
STP, ScTP | S/UTP | braiding | none |
S-FTP, SFTP, STP | SF/UTP | braiding, foil | none |
FFTP | F/FTP | foil | foil |
SSTP, SFTP, STP PiMF | S/FTP | braiding | foil |
The code before the slash designates the shielding for the cable itself, while the code after the slash determines the shielding for the individual pairs:
Name | Typical construction | Bandwidth | Applications | Notes |
Level 1 | 0.4 MHz | Telephone and modem lines | Not described in EIA/TIA recommendations. Unsuitable for modern systems.[7] | |
Level 2 | 4 MHz | Older terminal systems, e.g. IBM 3270 | Not described in EIA/TIA recommendations. Unsuitable for modern systems.[7] | |
Cat.3 | UTP[8] | 16 MHz[8] | 10BASE-T and 100BASE-T4 Ethernet[8] | Described in EIA/TIA-568. Unsuitable for speeds above 16 Mbit/s. Now mainly for telephone cables[8] |
Cat.4 | UTP[8] | 20 MHz[8] | 16 Mbit/s[8] Token Ring | Not commonly used[8] |
Cat.5 | UTP[8] | 100 MHz[8] | 100BASE-TX & 1000BASE-T Ethernet[8] | Common in most current LANs[8] |
Cat.5e | UTP[8] | 100 MHz[8] | 100BASE-TX & 1000BASE-T Ethernet[8] | Enhanced Cat5. Same construction as Cat5, but with better testing standards. |
Cat.6 | UTP[8] | 250 MHz[8] | 10GBASE-T Ethernet | Most commonly installed cable in Finland according to the 2002 standard. SFS-EN 50173-1 |
Cat.6a | U/FTP, F/UTP | 500 MHz | 10GBASE-T Ethernet | Adds cable shielding. ISO/IEC 11801:2002 Amendment 2. |
Cat.7 | F/FTP, S/FTP | 600 MHz | Telephone, CCTV, 1000BASE-TX in the same cable. 10GBASE-T Ethernet. | Fully shielded cable. ISO/IEC 11801 2nd Ed. |
Cat.7a | F/FTP, S/FTP | 1000 MHz | Telephone, CATV, 1000BASE-TX in the same cable. 10GBASE-T Ethernet. | Uses all four pairs. ISO/IEC 11801 2nd Ed. Am. 2. |
Cat.8.1 | U/FTP, F/UTP | 1600-2000 MHz | Telephone, CATV, 1000BASE-TX in the same cable. 40GBASE-T Ethernet. | In development. |
Cat.8.2 | F/FTP, S/FTP | 1600-2000 MHz | Telephone, CATV, 1000BASE-TX in the same cable. 40GBASE-T Ethernet. | In development. |
A solid core cable uses one solid wire per conductor and in a four pair cable there would be a total of eight solid wires.[8] Stranded conductor uses multiple wires wrapped around each other in each conductor and in a four pair with seven strands per conductor cable, there would be a total of 56 wires (2 per pair x 4 pairs x 7 strands).[8]
Solid core cable is supposed to be used for permanently installed runs. It is less flexible than stranded cable and is more prone to failure if repeatedly flexed. Stranded cable is used for fly leads at patch panel and for connections from wall-ports to end devices, as it resists cracking of the conductors.
Connectors need to be designed differently for solid core than for stranded. Use of a connector with the wrong cable type is likely to lead to unreliable cabling. Plugs designed for solid and stranded core are readily available, and some vendors even offer plugs designed for use with both types. The punch-down blocks on patch-panel and wall port jacks are designed for use with solid core cable.
Wikimedia Commons has media related to Twisted-pair cables. |