Characterization of a thermally imidized soluble polyimide film

A soluble aromatic poly(amic acid) film was converted to a soluble polyimide by staging at 25 deg intervals to 325 C and characterized at each interval by several analytical methods. The behavior observed was consistent with an interpretation that a reduction occurred in molecular weight of the poly(amic acid) during the initial stages of cure before the ultimate molecular weight was achieved as a polyimide. This interpretation was supported by the results of solution viscosity, gel permeation chromatography, low angle laser light scattering photometry and infrared spectroscopy analysis. The results serve to increase the fundamental understanding of how polyimides are thermally formed from poly(amic acids)

Tip-splitting evolution in the idealized Saffman-Taylor problem

We derive a formula describing the evolution of tip-splittings of Saffman-Taylor fingers in a Hele-Shaw cell, at zero surface tension

Reversible photonic hydrogel sensors via holographic interference lithography

Continuous monitoring of physiological conditions and biomarkers via optical holographic sensors is an area of growing interest to facilitate the expansion of personalised medicine. Here, a facile laser-induced dual polymerization method is developed to fabricate holographic hydrogel sensors for the continuous and reversible colorimetric determination of pH variations over a physiological range in serum (pH 7–9). Readout parameters simulated through a Finite-difference time-domain Yee's algorithm retrieve the spectral response through expansion. Laser lithography of holographic hydrogel sensor fabrication is achieved via a single 355 nm laser pulse to initiate polymerization of ultrafine hydrogel fringes. Eliminating the requirement for complex processing of toxic components and streamlining the synthetic procedure provides a simpler route to mass production. Optimised pH-responsive hydrogels contain amine bearing functional co-monomers demonstrating reversible Bragg wavelength shifts of 172 nm across the entire visible wavelength range with pH variation from 7.0 to 9.0 upon illumination with broadband light. Photolithographic recording of information shows the ability to convey detailed information to users for qualitative identification of pH. Holographic sensor reversibility over 20 cycles showed minimal variation in replay wavelength supporting reliable and consistent readout, with optimised sensors showing rapid response times of <5 min. The developed sensors demonstrate the application to continuous monitoring in biological fluids, withstanding interference from electrolytes, saccharides, and proteins colorimetrically identifying bovine serum pH over a physiological range. The holographic sensors benefit point-of-care pH analysis of biological analytes which could be applied to the identification of blood gas disorders and wound regeneration monitoring through colorimetric readouts

Self-similarity in Laplacian Growth

We consider Laplacian Growth of self-similar domains in different geometries. Self-similarity determines the analytic structure of the Schwarz function of the moving boundary. The knowledge of this analytic structure allows us to derive the integral equation for the conformal map. It is shown that solutions to the integral equation obey also a second order differential equation which is the one dimensional Schroedinger equation with the sinh inverse square potential. The solutions, which are expressed through the Gauss hypergeometric function, characterize the geometry of self-similar patterns in a wedge. We also find the potential for the Coulomb gas representation of the self-similar Laplacian growth in a wedge and calculate the corresponding free energy.Comment: 16 pages, 9 figure

Summer Distribution of Bowhead Whales, Balaena mysticetus, Relative to Oil Industry Activities in the Canadian Beaufort Sea, 1980-84

Aerial surveys in 1980-84 showed that summer distribution of bowheads in the Beaufort Sea varied markedly between years. Distribution varied both outside and within the "main industrial area" (MIA), the area of island construction, drilling and intensive ship and helicopter traffic. Numbers of bowheads in the MIA were high in 1980, lower in 1981, near zero in 1982 and very low in 1983-84. The few whales in the MIA in 1983-84 were mainly near its edges, contrary to 1980-81. These data, plus limited evidence from 1976-79, indicate that bowheads were numerous in the centre of the MIA in 3 of 5 years from 1976-80 (1976-77, 1980) vs. 0 of 4 years from 1981-84. One hypothesis is that progressively increasing industrial activities affected bowhead distribution after 1980. However, bowheads probably also react to variations in their zooplankton prey, which may be affected by year-to-year changes in oceanography and weather. Influences of natural factors on zooplankton and bowheads need to be better understood in order to assess whether oil exploration caused any of the observed changes in bowhead distribution.Key words: bowhead whale, Balaena mysticetus, Beaufort Sea, oil exploration, seismic exploration, aerial surveysDes relev&eacute;s a&eacute;riens effectu&eacute;s entre 1980 et 1984 ont montr&eacute; que la r&eacute;partition estivale des baleines franches dans la mer de Beaufort varie nettement d&rsquo;ann&eacute;e en ann&eacute;e. Elle varie &agrave; fois &agrave; l&rsquo;ext&eacute;rieure et &agrave; l&rsquo;int&eacute;rieur de la &ldquo;zone industrielle principale&rdquo; (ZIP), qui est la zone de construction de l&rsquo;&icirc;le, de forage et de circulation intense de bateaux et d&rsquo;h&eacute;licopt&egrave;res. Le nombre de baleines franches dans la ZIP &eacute;tait &eacute;lev&eacute; en 1980, plus bas en 1981, pr&egrave;s de z&eacute;ro en 1982, et tr&egrave;s bas en 1983 et 1984. Les quelques baleines pr&eacute;sentes dans la ZIP en 1983 et 1984 &eacute;taient principalement &agrave; la p&eacute;riph&eacute;rie, contrairement &agrave; 1980 et 1981. Ces donn&eacute;es, jointes &agrave; des &eacute;vidences plus limit&eacute;es de 1976 &agrave; 1979, indiquent que les baleines franches &eacute;taient nombreuses au centre de la ZIP pendant 3 ann&eacute;es sur 5, allant de 1976 &agrave; 1980 (1976, 1977 et 1980), par rapport &agrave; aucune ann&eacute;e sur les quatre allant de 1981 &agrave; 1984. On avance l&rsquo;hypoth&egrave;se que les activit&eacute;s industrielles progressivement croissantes ont affect&eacute; la r&eacute;partition des baleines franches apr&egrave;s 1980. Cependant, les baleines franches ont probablement r&eacute;agi aussi aux variations de zooplancton qui constitue leur nourriture et qui peut &ecirc;tre affect&eacute; par les changements qui ont lieu d&rsquo;ann&eacute;e en ann&eacute;e dans l&rsquo;oc&eacute;anographie et le climat. I1 est n&eacute;cessaire de mieux comprendre l&rsquo;influence des facteurs naturels sur le zooplancton et les baleines franches afin d&rsquo;&eacute;valuer si l&rsquo;exploration p&eacute;troli&egrave;re a provoqu&eacute; l&rsquo;un quelconque des changements observ&eacute;s dans la r&eacute;partition de ces baleines.Mots cl&eacute;s: baleine franche, Balaena mysticetus, mer de Beaufort, exploration p&eacute;troli&egrave;re, exploration sismique, relev&eacute;s a&eacute;rien

Detecting delirium superimposed on dementia: diagnostic accuracy of a simple combined arousal and attention testing procedure

Detecting delirium superimposed on dementia (DSD) can be challenging because assessment partly relies on cognitive tests that may be abnormal in both conditions. We hypothesized that a combined arousal and attention testing procedure would accurately detect DSD. Patients aged ≥70 years were recruited from five hospitals across Europe. Delirium was diagnosed by physicians using DSM-5 criteria using information from nurses, carers, and medical records. Dementia was ascertained by the Informant Questionnaire on Cognitive Decline in the Elderly. Arousal was measured using the Observational Scale of Level of Arousal (OSLA), which assesses eye opening, eye contact, posture, movement, and communication. Attention was measured by participants signaling each time an “A” was heard when “S-A-V-E-A-H-A-A-R-T” was read out. The sample included 114 persons (mean age 82 years (SD 7); 54% women). Dementia alone was present in 25% (n = 28), delirium alone in 18% (n = 21), DSD in 27% (n = 31), and neither in 30% (n = 34). Arousal and attention was assessed in n = 109 (96%). Using OSLA, 83% participants were correctly identified as having delirium (sensitivity 85%, specificity 82%, AUROC 0.92). The attention task correctly classified 76% of participants with delirium (sensitivity 90%, specificity 64%, AUROC 0.80). Combining scores correctly classified 91% of participants with delirium (sensitivity 84%, specificity 92%, AUROC 0.94). Diagnostic accuracy remained high in the subgroup with dementia (93% correctly classified, sensitivity 94%, specificity 92%, AUROC 0.98). This combined arousal–attention assessment to detect DSD was brief yet had high diagnostic accuracy. Such an approach could have clinical utility for diagnosing DSD

Growth processes related to the dispersionless Lax equations

This paper is a short review of the connection between certain types of growth processes and the integrable systems theory, written from the viewpoint of the latter. Starting from the dispersionless Lax equations for the 2D Toda hierarchy, we interpret them as evolution equations for conformal maps in the plane. This provides a unified approach to evolution of smooth domains (such as Laplacian growth) and growth of slits. We show that the L\"owner differential equation for a parametric family of conformal maps of slit domains arises as a consistency condition for reductions of the dispersionless Toda hierarchy. It is also demonstrated how the both types of growth processes can be simulated by the large $N$ limit of the Dyson gas picture for the model of normal random matrices.Comment: 16 pages, 2 figures, typos corrected, references adde

Constraints on the perturbed mutual motion in Didymos due to impact-induced deformation of its primary after the DART impact

Binary near-Earth asteroid (65803) Didymos is the target of the proposed NASA Double Asteroid Redirection Test (DART), part of the Asteroid Impact & Deflection Assessment (AIDA) mission concept. In this mission, the DART spacecraft is planned to impact the secondary body of Didymos, perturbing mutual dynamics of the system. The primary body is currently rotating at a spin period close to the spin barrier of asteroids, and materials ejected from the secondary due to the DART impact are likely to reach the primary. These conditions may cause the primary to reshape, due to landslides, or internal deformation, changing the permanent gravity field. Here, we propose that if shape deformation of the primary occurs, the mutual orbit of the system would be perturbed due to a change in the gravity field. We use a numerical simulation technique based on the full two-body problem to investigate the shape effect on the mutual dynamics in Didymos after the DART impact. The results show that under constant volume, shape deformation induces strong perturbation in the mutual motion. We find that the deformation process always causes the orbital period of the system to become shorter. If surface layers with a thickness greater than ~0.4 m on the poles of the primary move down to the equatorial region due to the DART impact, a change in the orbital period of the system and in the spin period of the primary will be detected by ground-based measurement.Comment: 8 pages, 7 figures, 2 tables, accepted for publication in MNRA