814 research outputs found
LightBox: a multiwell plate illumination system for photoactive molecule characterization
Multiwell plates (MWPs) are the workhorses of the life sciences. However, biophotonics research with MWPs is limited, in part due to the lack of equipment suitable for photoâirradiation of photoactive molecules in a MWPâsuitable, highâthroughput manner, either commercially or through openâsource MWP systems. Here we present âLightBoxâ, a calibrated controllable MWP illumination system with broad applications including screening of photoactive molecules and characterization of photocatalytic chemicals. LightBox is a high intensity, accurately controllable, uniform illumination system designed for MWPs with electronics and a control unit that provides a simple and intuitive interface. LightBox can reach intensities of 0.23âmW/mm2 at wavelengths of 405ânm with variance between well sites of <5%. The usefulness of LightBox is demonstrated by assessing the IC50 of a photosensitizing compound using a live/dead assay following simultaneous irradiation of the sample at a range of concentrations, eliminating uncontrolled variables between concentrations and drastically increasing assessment speed
A Derivation of Three-Dimensional Inertial Transformations
The derivation of the transformations between inertial frames made by
Mansouri and Sexl is generalised to three dimensions for an arbitrary direction
of the velocity. Assuming lenght contraction and time dilation to have their
relativistic values, a set of transformations kinematically equivalent to
special relativity is obtained. The ``clock hypothesis'' allows the derivation
to be extended to accelerated systems. A theory of inertial transformations
maintaining an absolute simultaneity is shown to be the only one logically
consistent with accelerated movements. Algebraic properties of these
transformations are discussed. Keywords: special relativity, synchronization,
one-way velocity of light, ether, clock hypothesis.Comment: 16 pages (A5), Latex, one figure, to be published in Found. Phys.
Lett. (1997
Computerâaided photoâidentification of a rare stingray, Megatrygon microps
We have defined protocol for photoâidentification to identify individual Megatrygon microps. 104 identification photographs were taken between 2005 and 2019. Spot patterns on the dorsal surface were used to identify individuals. Unique scarring on 8 reâobserved M. microps provided an independent confirmation of pattern stability of up to 761âdays. Previously, studies have lacked statistical testing to validate photoâidentification approach. The I3S photoâmatching software was proven to successfully match images, identifying 69 individuals. A photoâmatching software facilitates an openâsource platform for identifying individual M. microps, allowing for better population assessments
Dietary iron intakes based on food composition data may underestimate the contribution of potentially exchangeable contaminant iron from soil
Iron intakes calculated from one-day weighed records were compared with those from same day analyzed duplicate diet composites collected from 120 Malawian women living in two rural districts with contrasting soil mineralogy and where threshing may contaminate cereals with soil iron. Soils and diet composites from the two districts were then subjected to a simulated gastrointestinal digestion and iron availability in the digests measured using a Caco-2 cell model. Median analyzed iron intakes (mg/d) were higher (p < 0.001) than calculated intakes in both Zombwe (16.6 vs. 10.1 mg/d) and Mikalango (29.6 vs. 19.1 mg/d), attributed to some soil contaminant iron based on high Al and Ti concentrations in diet composites. A small portion of iron in acidic soil from Zombwe, but not Mikalango calcareous soil, was bioavailable, as it induced ferritin expression in the cells, and may have contributed to higher plasma ferritin and total body iron for the Zombwe women reported earlier, despite lower iron intakes. In conclusion, iron intakes calculated from food composition data were underestimated, highlighting the importance of analyzing duplicate diet composites where extraneous contaminant iron from soil is likely. Acidic contaminant soil may make a small but useful contribution to iron nutrition
Recommendations for services for people with living with chronic breathlessness in advanced disease: results of a transparent expert consultation
Chronic breathlessness is highly distressing for people with advanced disease and their informal carers, yet health services for this group remain highly heterogeneous. We aimed to generate evidence-based stakeholder-endorsed recommendations for practice, policy and research concerning services for people with advanced disease and chronic breathlessness. We used transparent expert consultation, comprising modified nominal group technique during a stakeholder workshop, and an online consensus survey. Stakeholders, representing multiple specialities and professions, and patient/carers were invited to participate. Thirty-seven participants attended the stakeholder workshop and generated 34 separate recommendations, rated by 74 online survey respondents. Seven recommendations had strong agreement and high levels of consensus. Stakeholders agreed services should be person-centred and flexible, should cut across multiple disciplines and providers and should prioritize breathlessness management in its own right. They advocated for wide geographical coverage and access to expert care, supported through skills-sharing among professionals. They also recommended recognition of informal carers and their role by clinicians and policymakers. Overall, stakeholders' recommendations reflect the need for improved access to person-centred, multi-professional care and support for carers to provide or access breathlessness management interventions. Future research should test the optimal models of care and educational strategies to meet these recommendations
Exceptionally Slow Rise in Differential Reflectivity Spectra of Excitons in GaN: Effect of Excitation-induced Dephasing
Femtosecond pump-probe (PP) differential reflectivity spectroscopy (DRS) and
four-wave mixing (FWM) experiments were performed simultaneously to study the
initial temporal dynamics of the exciton line-shapes in GaN epilayers. Beats
between the A-B excitons were found \textit{only for positive time delay} in
both PP and FWM experiments. The rise time at negative time delay for the
differential reflection spectra was much slower than the FWM signal or PP
differential transmission spectroscopy (DTS) at the exciton resonance. A
numerical solution of a six band semiconductor Bloch equation model including
nonlinearities at the Hartree-Fock level shows that this slow rise in the DRS
results from excitation induced dephasing (EID), that is, the strong density
dependence of the dephasing time which changes with the laser excitation
energy.Comment: 8 figure
Effective interaction between helical bio-molecules
The effective interaction between two parallel strands of helical
bio-molecules, such as deoxyribose nucleic acids (DNA), is calculated using
computer simulations of the "primitive" model of electrolytes. In particular we
study a simple model for B-DNA incorporating explicitly its charge pattern as a
double-helix structure. The effective force and the effective torque exerted
onto the molecules depend on the central distance and on the relative
orientation. The contributions of nonlinear screening by monovalent counterions
to these forces and torques are analyzed and calculated for different salt
concentrations. As a result, we find that the sign of the force depends
sensitively on the relative orientation. For intermolecular distances smaller
than it can be both attractive and repulsive. Furthermore we report a
nonmonotonic behaviour of the effective force for increasing salt
concentration. Both features cannot be described within linear screening
theories. For large distances, on the other hand, the results agree with linear
screening theories provided the charge of the bio-molecules is suitably
renormalized.Comment: 18 pages, 18 figures included in text, 100 bibliog
Testing "microscopic" theories of glass-forming liquids
We assess the validity of "microscopic" approaches of glass-forming liquids
based on the sole k nowledge of the static pair density correlations. To do so
we apply them to a benchmark provided by two liquid models that share very
similar static pair density correlation functions while disp laying distinct
temperature evolutions of their relaxation times. We find that the approaches
are unsuccessful in describing the difference in the dynamical behavior of the
two models. Our study is not exhausti ve, and we have not tested the effect of
adding corrections by including for instance three-body density correlations.
Yet, our results appear strong enough to challenge the claim that the slowd own
of relaxation in glass-forming liquids, for which it is well established that
the changes of the static structure factor with temperature are small, can be
explained by "microscopic" appr oaches only requiring the static pair density
correlations as nontrivial input.Comment: 10 pages, 7 figs; Accepted to EPJE Special Issue on The Physics of
Glasses. Arxiv version contains an addendum to the appendix which does not
appear in published versio
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