Because the literature relating to the influence of degeneration on the viscoelasticity and tissue composition of human lateral menisci remains contradictory or completely lacking, the aim of this ...study was to fill these gaps by comprehensively characterising the biomechanical properties of menisci with regard to the degree of degeneration.
Meniscal tissue from 24 patients undergoing a total knee replacement was collected and the degeneration of each region classified according to Pauli et al. For biomechanical characterisation, compression and tensile tests were performed. Additionally, the water content was determined and infrared (IR) spectroscopy was applied to detect changes in the structural composition, particularly of the proteoglycan and collagen content.
With an increasing degree of degeneration, a significant decrease of the equilibrium modulus was detected, while simultaneously the water content and the hydraulic permeability significantly increased. However, the tensile modulus displayed a tendency to decrease with increasing degeneration, which might be due to the significantly decreasing amount of collagen content identified by the IR measurements.
The findings of the current study may contribute to the understanding of meniscus degeneration, showing that degenerative processes appear to mainly worsen viscoelastic properties of the inner circumference by disrupting the collagen integrity.
The menisci protect the articular cartilage by reducing contact pressure in the knee. To restore their function after injury, a new silk fibroin replacement scaffold was developed. To elucidate its ...tribological properties, friction of the implant was tested against cartilage and glass, where the latter is typically used in tribological cartilage studies. The silk scaffold exhibited a friction coefficient against cartilage of 0.056, which is higher than meniscus against cartilage but in range of the requirements for meniscal replacements. Further, meniscus friction against glass was lower than cartilage against glass, which correlated with the surface lubricin content. Concluding, the tribological properties of the new material suggest a possible long-term chondroprotective function. In contrast, glass always produced high, non-physiological friction coefficients.
•A new silk fibroin scaffold provides low friction coefficient against articular cartilage.•A high friction coefficient is observed when tested against glass due to the missing interstitial fluid load support.•Friction studies of non-biological materials, e.g. for implants, should be carried out against articular cartilage.•Meniscus has a higher lubricin content on its surface in comparison to articular cartilage.
The global polarization of Λ hyperons along the total orbital angular momentum of a relativistic heavy-ion collision is presented based on the high statistics data samples collected in Au+Au ...collisions at sNN=2.4 GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at GSI, Darmstadt. This is the first measurement below the strangeness production threshold in nucleon-nucleon collisions. Results are reported as a function of the collision centrality as well as a function of the hyperon's transverse momentum (pT) and rapidity (yCM) for the range of centrality 0–40%. We observe a strong centrality dependence of the polarization with an increasing signal towards peripheral collisions. For mid-central (20 – 40%) collisions the polarization magnitudes are 〈PΛ〉(%)=6.8±1.3(stat.)±2.1(syst.) for Au+Au and 〈PΛ〉(%)=6.2±0.4(stat.)±0.6(syst.) for Ag+Ag, which are the largest values observed so far. This observation thus provides a continuation of the increasing trend previously observed by STAR and contrasts expectations from recent theoretical calculations predicting a maximum in the region of collision energies about 3 GeV. The observed polarization is of a similar magnitude as predicted by 3D-fluid-dynamics and the UrQMD plus thermal vorticity model and significantly above results from the AMPT model.
Laccases are multicopper enzymes that catalyze oxidation of electron-rich substrates coupled to reduction of molecular oxygen to water. Since the Type 1 copper (T1 Cu) is the site where electrons are ...withdrawn from the substrate, it is assumed that the reduction potential of this copper correlates with enzyme activity. Herein, we studied the correlation of the T1 Cu reduction potential and the enzymatic activity of the small two-domain laccase Ssl1 from Streptomyces sviceus. For a systematic approach, we aimed to minimize any effects other than the reduction potential difference. To this end, we constructed a series of Ssl1 mutants with reduction potentials varying from <290 to 560 mV. Along with the hydrophobicity of the axial ligand of the T1 Cu also structural changes in the substrate binding site and additional hydrogen bonding increased the reduction potential. Enzyme activity experiments demonstrated that the T1 Cu reduction potential has a different effect on oxidation of different substrates. Whereas there was no obvious correlation between the T1 Cu reduction potential and kinetic parameters for the oxidation of syringaldazine (with a reduction potential of 390 mV), a good correlation was observed between the T1 Cu reduction potential and the conversion of substituted phenols with reduction potentials between 660 and 820 mV. This correlation was pronounced for the Ssl1 variants with reduction potentials above 470 mV, which demonstrated increased activities also during the oxidation of two dyes, alizarin red S and indigo carmine.
How the environment of the Type 1 copper of a laccase influences the enzyme activity remains an intriguing question. In this work, we constructed mutants of a small laccase from Streptomyces sviceus with reduction potentials ranging from <290 to 560 mV, and evaluated their activity towards high- and low-potential substrates. Display omitted
•Mutants of Ssl1 laccase with reduction potentials between <290 and 560 mV were constructed.•Reduction potential of the Type 1 copper (T1 Cu) correlated with the axial ligand hydrophobicity.•Activity towards substituted phenols correlated with the T1 Cu reduction potential.•Ssl1 variant with a reduction potential of 560 mV oxidized substrates not accepted by wild type.
A feasibility study has been performed in order to investigate the performance of the HADES detector to measure the electromagnetic decays of the hyperon resonances
Σ
(
1385
)
0
,
Λ
(
1405
)
and
...Λ
(
1520
)
as well as the production of double strange baryon systems
Ξ
-
and
Λ
Λ
in p + p reactions at a beam kinetic energy of
4.5
GeV
. The existing HADES detector will be upgraded by a new Forward Detector, which extends the detector acceptance into a range of polar angles that plays a crucial role for these investigations. The analysis of each channel is preceded by a consideration of the production cross-sections. Afterwards the expected signal count rates using a target consisting of either liquid hydrogen or polyethylene are summarized.
Hadron production (
π
±
, proton,
Λ
,
K
S
0
,
K
±
) in
π
-
+
C
and
π
-
+
W
collisions is investigated at an incident pion beam momentum of
1.7
GeV
/
c
. This comprehensive set of data measured with ...HADES at SIS18/GSI significantly extends the existing world data on hadron production in pion induced reactions and provides a new reference for models that are commonly used for the interpretation of heavy-ion collisions. The measured inclusive differential production cross-sections are compared with state-of-the-art transport model (GiBUU, SMASH) calculations. The (semi-) exclusive channel
π
-
+
A
→
Λ
+
K
S
0
+
X
, in which the kinematics of the strange hadrons are correlated, is also investigated and compared to a model calculation. Agreement and remaining tensions between data and the current version of the considered transport models are discussed.
The production of
Σ
0
hyperons in proton proton collisions at a beam kinetic energy of 3.5 GeV impinging on a liquid hydrogen target was investigated using data collected with the HADES setup. The ...total production cross section is found to be
σ
(
p
K
+
Σ
0
)
=
17.7
±
1.7
(
s
t
a
t
)
±
1.6
(
s
y
s
t
)
µb. Differential cross section distributions of the exclusive channel
p
p
→
p
K
+
Σ
0
were analyzed in the center-of-mass, Gottfried–Jackson and helicity reference frames for the first time at the excess energy of 556 MeV. The data support the interplay between pion and kaon exchange mechanisms and clearly demonstrate the contribution of interfering nucleon resonances decaying to
K
+
Σ
0
. The Bonn–Gatchina partial wave analysis was employed to analyse the data. Due to the limited statistics, it was not possible to obtain an unambiguous determination of the relative contribution of intermediate nucleon resonances to the final state. However nucleon resonances with masses around 1.710
GeV
/
c
2
(
N
∗
(
1710
)
) and 1.900
GeV
/
c
2
(
N
∗
(
1900
)
or
Δ
∗
(
1900
)
) are preferred by the fit.
Abstract The production of $$\Sigma ^{0}$$ Σ 0 hyperons in proton proton collisions at a beam kinetic energy of 3.5 GeV impinging on a liquid hydrogen target was investigated using data collected ...with the HADES setup. The total production cross section is found to be $${\sigma (pK^{+}\Sigma ^{0}) = 17.7 \pm 1.7 (stat) \pm 1.6 (syst)}$$ σ ( p K + Σ 0 ) = 17.7 ± 1.7 ( s t a t ) ± 1.6 ( s y s t ) µb. Differential cross section distributions of the exclusive channel $${pp \rightarrow pK^{+}\Sigma ^{0}}$$ p p → p K + Σ 0 were analyzed in the center-of-mass, Gottfried–Jackson and helicity reference frames for the first time at the excess energy of 556 MeV. The data support the interplay between pion and kaon exchange mechanisms and clearly demonstrate the contribution of interfering nucleon resonances decaying to $$\textrm{K}^{+}\Sigma ^{0}$$ K + Σ 0 . The Bonn–Gatchina partial wave analysis was employed to analyse the data. Due to the limited statistics, it was not possible to obtain an unambiguous determination of the relative contribution of intermediate nucleon resonances to the final state. However nucleon resonances with masses around 1.710 $${\textrm{GeV}/\textrm{c}^{2}}$$ GeV / c 2 ( $${\textrm{N}^{*}(1710)}$$ N ∗ ( 1710 ) ) and 1.900 $${\textrm{GeV}/\textrm{c}^{2}}$$ GeV / c 2 ( $${\textrm{N}^{*}(1900)}$$ N ∗ ( 1900 ) or $${\Delta ^{*}(1900)}$$ Δ ∗ ( 1900 ) ) are preferred by the fit.
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