Reversible magnetomechanical collapse: virtual touching and detachment of rigid inclusions in a soft elastic matrix

Soft elastic composite materials containing particulate rigid inclusions in a soft elastic matrix are candidates for developing soft actuators or tunable damping devices. The possibility to reversibly drive the rigid inclusions within such a composite together to a close-to-touching state by an external stimulus would offer important benefits. Then, a significant tuning of the mechanical properties could be achieved due to the resulting mechanical hardening. For a long time, it has been argued whether a virtual touching of the embedded magnetic particles with subsequent detachment can actually be observed in real materials, and if so, whether the process is reversible. Here, we present experimental results that demonstrate this phenomenon in reality. Our system consists of two paramagnetic nickel particles embedded at finite initial distance in a soft elastic polymeric gel matrix. Magnetization in an external magnetic field tunes the magnetic attraction between the particles and drives the process. We quantify the scenario by different theoretical tools, i.e., explicit analytical calculations in the framework of linear elasticity theory, a projection onto simplified dipole-spring models, as well as detailed finite-element simulations. From these different approaches, we conclude that in our case the cycle of virtual touching and detachment shows hysteretic behavior due to the mutual magnetization between the paramagnetic particles. Our results are important for the design and construction of reversibly tunable mechanical damping devices. Moreover, our projection on dipole-spring models allows the formal connection of our description to various related systems, e.g., magnetosome filaments in magnetotactic bacteria.Comment: 14 pages, 7 figure

Gender-dependent differences in plasma matrix metalloproteinase-8 elevated in pulmonary tuberculosis.

Tuberculosis (TB) remains a global health pandemic and greater understanding of underlying pathogenesis is required to develop novel therapeutic and diagnostic approaches. Matrix metalloproteinases (MMPs) are emerging as key effectors of tissue destruction in TB but have not been comprehensively studied in plasma, nor have gender differences been investigated. We measured the plasma concentrations of MMPs in a carefully characterised, prospectively recruited clinical cohort of 380 individuals. The collagenases, MMP-1 and MMP-8, were elevated in plasma of patients with pulmonary TB relative to healthy controls, and MMP-7 (matrilysin) and MMP-9 (gelatinase B) were also increased. MMP-8 was TB-specific (p<0.001), not being elevated in symptomatic controls (symptoms suspicious of TB but active disease excluded). Plasma MMP-8 concentrations inversely correlated with body mass index. Plasma MMP-8 concentration was 1.51-fold higher in males than females with TB (p<0.05) and this difference was not due to greater disease severity in men. Gender-specific analysis of MMPs demonstrated consistent increase in MMP-1 and -8 in TB, but MMP-8 was a better discriminator for TB in men. Plasma collagenases are elevated in pulmonary TB and differ between men and women. Gender must be considered in investigation of TB immunopathology and development of novel diagnostic markers

Risk perception about medication sharing among patients: a focus group qualitative study on borrowing and lending of prescription analgesics

Filipa Markotic,1 Davorka Vrdoljak,2 Marijana Puljiz,3 Livia Puljak,4 1Centre for Clinical Pharmacology, University Clinical Hospital Mostar, Mostar, Bosnia and Herzegovina; 2Department of Family Medicine, University of Split School of Medicine, Split, 3Family Medicine Clinic, Health Centre Imotski, Kamenmost, 4Laboratory for Pain Research, University of Split School of Medicine, Split, Croatia Background: One form of self-medication is sharing of medications, defined as borrowing or lending medications in situations where the receiver of these drugs is not the individual to whom the medications were allocated. Objective: To explore experiences and opinions of patients about sharing prescription analgesics, reasons for sharing prescription analgesics, the way in which patients choose to share those medications, their awareness of risk regarding sharing prescription analgesics, and how they estimated the potential risk.Methods: This qualitative study was conducted by focus group discussions with 40 participants led by a moderator trained in focus group methodology using a semi-structured moderator guide. Adults aged &ge;18 years who had received a prescription for an analgesic at least once in a lifetime were included. Six separate focus groups were conducted to discuss participants&rsquo; perception of risks associated with sharing of prescription analgesics among patients. Additionally, participants filled out two questionnaires on demographic data, their own behavior regarding sharing analgesics, and their attitudes about risks associated with sharing prescription analgesics.Results: In a questionnaire, 55% of the participants indicated that they personally shared prescription analgesics, while subsequently in the focus group discussions, 76% confessed to such behavior. Participants recognized certain risks related to sharing of prescription analgesics, mentioned a number of reasons for engaging in such behavior, and indicated certain positive aspects of such behavior. Forty-five percent of the participants indicated that sharing prescription analgesics is riskier than sharing nonprescription analgesics.Conclusion: There is a prevalent attitude among participants that sharing prescription analgesics is a positive behavior, where potential benefits outweigh risks. Keywords: pain, self-medication, drugs, risk awareness, risk estimatio