Lassoing saddle splay and the geometrical control of topological defects

Systems with holes, such as colloidal handlebodies and toroidal droplets, have been studied in the nematic liquid crystal (NLC) 4-cyano-4'-pentylbiphenyl (5CB): both point and ring topological defects can occur within each hole and around the system, while conserving the system's overall topological charge. However, what has not been fully appreciated is the ability to manipulate the hole geometry with homeotropic (perpendicular) anchoring conditions to induce complex, saddle-like deformations. We exploit this by creating an array of holes suspended in an NLC cell with oriented planar (parallel) anchoring at the cell boundaries. We study both 5CB and a binary mixture of bicyclohexane derivatives (CCN-47 and CCN-55). Through simulations and experiments, we study how the bulk saddle deformations of each hole interact to create novel defect structures, including an array of disclination lines, reminiscent of those found in liquid crystal blue phases. The line locations are tunable via the NLC elastic constants, the cell geometry, and the size and spacing of holes in the array. This research lays the groundwork for the control of complex elastic deformations of varying length scales via geometrical cues in materials that are renowned in the display industry for their stability and easy manipulability.Comment: 9 pages, 7 figures, 1 supplementary figur

Red- and Near-Infrared-Excited Autofluorescence as a Marker for Acute Oxidative Stress in Skin Exposed to Cigarette Smoke Ex Vivo and In Vivo

Air pollution is increasing worldwide and skin is exposed to high levels of pollution daily, causing oxidative stress and other negative consequences. The methods used to determine oxidative stress in the skin are invasive and non-invasive label-free in vivo methods, which are severely limited. Here, a non-invasive and label-free method to determine the effect of cigarette smoke (CS) exposure on skin ex vivo (porcine) and in vivo (human) was established. The method is based on the measurement of significant CS-exposure-induced enhancement in red- and near-infrared (NIR)-excited autofluorescence (AF) intensities in the skin. To understand the origin of red- and NIR-excited skin AF, the skin was exposed to several doses of CS in a smoking chamber. UVA irradiation was used as a positive control of oxidative stress in the skin. The skin was measured with confocal Raman microspectroscopy before CS exposure, immediately after CS exposure, and after skin cleaning. CS exposure significantly increased the intensity of red- and NIR-excited skin AF in a dose-dependent manner in the epidermis, as confirmed by laser scanning microscopy AF imaging and fluorescence spectroscopy measurements. UVA irradiation enhanced the intensity of AF, but to a lower extent than CS exposure. We concluded that the increase in red- and NIR-excited AF intensities of the skin after CS exposure could clearly be related to the induction of oxidative stress in skin, where skin surface lipids are mainly oxidized

Change in Stripes for Cholesteric Shells via Anchoring in Moderation

Chirality, ubiquitous in complex biological systems, can be controlled and quantified in synthetic materials such as cholesteric liquid crystal (CLC) systems. In this work, we study spherical shells of CLC under weak anchoring conditions. We induce anchoring transitions at the inner and outer boundaries using two independent methods: by changing the surfactant concentration or by raising the temperature close to the clearing point. The shell confinement leads to new states and associated surface structures: a state where large stripes on the shell can be filled with smaller, perpendicular substripes, and a focal conic domain (FCD) state, where thin stripes wrap into at least two, topologically required, double spirals. Focusing on the latter state, we use a Landau–de Gennes model of the CLC to simulate its detailed configurations as a function of anchoring strength. By abruptly changing the topological constraints on the shell, we are able to study the interconversion between director defects and pitch defects, a phenomenon usually restricted by the complexity of the cholesteric phase. This work extends the knowledge of cholesteric patterns, structures that not only have potential for use as intricate, self-assembly blueprints but are also pervasive in biological systems

Tratamentul leziunilor aterosclerotice ale segmentului aorto-iliac prin by-pass de tip „crossover” în poziție ilio-femurală

Introduction. Atherosclerotic lesion of the aorto-ilio-femoral segment is a current problem for vascular surgery. Extra anatomical by-pass is an alternative method for revascularization of atherosclerotically affected limbs. The purpose of this method is to simplify major surgery. Objectives. Analysis of lower limb revascularization results by crossover bypass in ilio-femoral position. Materials and methods. Retrospective study within Republican Clinical Hospital „Timofei Moșneaga” from the Republic of Moldova, during the years 2017 - 2022 of patients with lower limb ischemia. The following aspects were analyzed: demographic data, location of anastomosis and perioperative complications. Results. This study included 32 patients. The male/female ratio was 31/1. Central anastomosis was applied on the external iliac artery in 71.8% (n = 23), commune iliac artery – 6.25% (n = 2), contralateral ilio-femoral bypass – 9.3% (n = 3), contralateral aorto-femoral bypass – 3.1% (n = 1), branch of aorto-bifemural bypass – 9.3% (n = 3). The distal anastomoses were applied on the on the deep femoral artery bifurcation of the common femoral artery – 65.6% (n = 21), on bifurcation of the common femoral artery in the rest of the cases. Perioperative complications included bypass thrombosis in two cases, intraoperative bladder injury – 1 case. Conclusion. Ilio-femoral bypasses are an alternative to classic method of revascularization in patients who cannot undergo endovascular or open abdominal surgery due to advanced cardiorespiratory pathology, hostile abdomen, porcelain aorta.Introducere. Afectarea aterosclerotică a segmentului aorto-ilio-femural este o problemă actuală pentru chirurgia vasculară. By-pass-urile extraanatomice sunt metode alternative pentru revascularizarea membrelor afectate aterosclerotic. Scopul acestei metode este simplificarea unei intervenții chirurgicale majore. Scopul lucrării. Analiza rezultatelor revascularizării membrului inferior prin bypass crossover în poziție ilio-femurală. Material și metode. Studiu retrospectiv în cadrul IMSP Spitalul Clinic Republican „Timofei Moșneaga” din Republica Moldova, în perioada anilor 2017-2022 a pacienților cu ischemia membrelor inferioare. Au fost analizate următoarele aspecte: date demografice, locul aplicării anastomozelor și complicațiile perioperatorii. Rezultate. În studiu au fost incluși 32 pacienți. Raportul bărbați/femei a fost 31/1. Anastomoza centrală a by-pass-ului a fost aplicată pe artera iliacă externă – în 71,8% (n = 23), pe artera iliaca comuna – 6,25% (n = 2), pe by-pass ilio-femural controlateral – 9,3%, pe by-pass aorto-femural controlateral – 3,1%, pe branșa by-passului aorto-bifemural – 9,3%. Anastomozele distale au fost aplicate pe artera femurală profundă – 65,6% (n = 21), în restul cazurilor – pe bifurcația arterei femurale comune. Complicațiile perioperatorii au fost: tromboza bypass-ului în 2 cazuri, lezarea vezicii urinare în timpul tunelării – 1 caz. Concluzii. By-pass-urile crossover în poziție ilio-femurală reprezintă o alternativă a intervențiilor chirurgicale clasice de revascularizare la pacienți care nu pot fi supuși intervențiilor endovasculare sau unei intervenții abdominale majore din cauza patologiei cardio-respiratorii avansate, abdomen ostil, aortă de porțelan

TREATMENT OF UNILATERAL ATHEROSCLEROTIC PROCESS OF THE AORTOILIAC SEGMENT BY CROSSOVER BYPASS IN ILIO-FEMORAL POSITION

Universitatea de Stat de Medicină şi Farmacie „Nicolae Testemiţanu”, Chişinău, Republica MoldovaIntroducere. Afectarea aterosclerotică a segmentului aorto-ilio-femural este o problemă actuală pentru chirurgia vasculară. By-pass-urile extraanatomice sunt metode alternative pentru revascularizarea membrelor afectate aterosclerotic. Scopul acestei metode este simplificarea unei intervenții chirurgicale majore. Scopul lucrării. Analiza rezultatelor revascularizării membrului inferior prin bypass crossover în poziție ilio-femurală. Material și metode. Studiu retrospectiv în cadrul IMSP Spitalul Clinic Republican „Timofei Moșneaga” din Republica Moldova, în perioada anilor 2017-2022 a pacienților cu ischemia membrelor inferioare. Au fost analizate următoarele aspecte: date demografice, locul aplicării anastomozelor și complicațiile perioperatorii. Rezultate. În studiu au fost incluși 32 pacienți. Raportul bărbați/femei a fost 31/1. Anastomoza centrală a by-pass-ului a fost aplicată pe artera iliacă externă – în 71,8% (n = 23), pe artera iliaca comuna – 6,25% (n = 2), pe by-pass ilio-femural controlateral – 9,3%, pe by-pass aorto-femural controlateral – 3,1%, pe branșa by-passului aorto-bifemural – 9,3%. Anastomozele distale au fost aplicate pe artera femurală profundă – 65,6% (n = 21), în restul cazurilor – pe bifurcația arterei femurale comune. Complicațiile perioperatorii au fost: tromboza bypass-ului în 2 cazuri, lezarea vezicii urinare în timpul tunelării – 1 caz. Concluzii. By-pass-urile crossover în poziție ilio-femurală reprezintă o alternativă a intervențiilor chirurgicale clasice de revascularizare la pacienți care nu pot fi supuși intervențiilor endovasculare sau unei intervenții abdominale majore din cauza patologiei cardio-respiratorii avansate, abdomen ostil, aortă de porțelan.Introduction. Atherosclerotic lesion of the aorto-ilio-femoral segment is a current problem for vascular surgery. Extra anatomical by-pass is an alternative method for revascularization of atherosclerotically affected limbs. The purpose of this method is to simplify major surgery. Objectives. Analysis of lower limb revascularization results by crossover bypass in ilio-femoral position. Materials and methods. Retrospective study within Republican Clinical Hospital „Timofei Moșneaga” from the Republic of Moldova, during the years 2017 - 2022 of patients with lower limb ischemia. The following aspects were analyzed: demographic data, location of anastomosis and perioperative complications. Results. This study included 32 patients. The male/female ratio was 31/1. Central anastomosis was applied on the external iliac artery in 71.8% (n = 23), commune iliac artery – 6.25% (n = 2), contralateral ilio-femoral bypass – 9.3% (n = 3), contralateral aorto-femoral bypass – 3.1% (n = 1), branch of aorto-bifemural bypass – 9.3% (n = 3). The distal anastomoses were applied on the on the deep femoral artery bifurcation of the common femoral artery – 65.6% (n = 21), on bifurcation of the common femoral artery in the rest of the cases. Perioperative complications included bypass thrombosis in two cases, intraoperative bladder injury – 1 case. Conclusion. Ilio-femoral bypasses are an alternative to classic method of revascularization in patients who cannot undergo endovascular or open abdominal surgery due to advanced cardiorespiratory pathology, hostile abdomen, porcelain aorta

Tratamentul leziunilor aterosclerotice ale segmentului aorto-iliac prin by-pass de tip „crossover" în poziţie ilio-femurală

Introducere. Afectarea aterosclerotică a segmentului aorto-ilio-femural este o problemă actuală pentru chirurgia vasculară. By-pass-urile extraanatomice sunt metode alternative pentru revascularizarea membrelor afectate aterosclerotic. Scopul acestei metode este simplificarea unei intervenţii chirurgicale majore. Scopul lucrării. Analiza rezultatelor revascularizării membrului inferior prin bypass crossover în poziţie ilio-femurală. Materiale și metode. Studiu retrospectiv în cadrul IMSP Spitalul Clinic Republican "Timofei Moșneaga" din Republica Moldova, în perioada anilor 2017-2022 a pacienţilor cu ischemia membrelor inferioare. Au fost analizate următoarele aspecte: date demografice, locul aplicării anastomozelor și complicaţiile perioperatorii. Rezultate. În studiu au fost incluşi 32 pacienţi. Raportul bărbaţi/femei a fost 31/1. Anastomoza centrală a by-pass-ului a fost aplicată pe artera iliacă externă - în 71,8% (n=23), pe artera iliacă comună - 6,25% (n=2), pe by-pass ilio-femural contralateral - 9,3%, pe by-pass aorto-femural contralateral -3,1%, pe branşa by-pass-ului aorto-bifemural - 9,3%. Anastomozele distale au fost aplicate pe artera femurală profundă - 65,6% (n=21), în restul cazurilor - pe bifurcaţia arterei femurale comune. Complicaţiile perioperatorii au fost: tromboza bypass-ului în 2 cazuri, lezarea vezicii urinare în timpul tunelării - 1 caz. Concluzii. By-pass-urile crossover în poziţie ilio-femurală reprezintă o alternativă a intervenţiilor chirurgicale clasice de revascularizare la pacienţi care nu pot fi supuşi intervenţiilor endovasculare sau unei intervenţii abdominale majore din cauza patologiei cardio-respiratorii avansate, abdomen ostil, aortă de porţelan

Evaluation of the influence of the hydraulic fluid temperature on power loss of the mining hydraulic excavator

In the steady state of operation, the temperature of a mining excavator hydraulic fluid is determined by the ambient temperature, hydraulic system design, and power losses. The amount of the hydraulic system power loss depends on the hydraulic fluid physical and thermodynamic properties and the degree of wear of the mining excavator hydraulic system working elements. The main causes of power losses are pressure losses in pipelines, valves and fittings, and leaks in pumps and hydraulic motors. With an increase in the temperature of hydraulic fluid, its viscosity decreases, which leads, on the one hand, to a decrease in power losses due to pressure losses in pipelines, valves and fittings, and, on the other hand, to an increase in volumetric leaks and associated power losses. To numerically determine the level of power losses occurring in the hydraulic system on an example of the Komatsu PC750-7 mining excavator when using Shell Tellus S2 V 22, 32, 46, 68 hydraulic oils with the corresponding kinematic viscosity of 22, 32, 46, 68 cSt at 40 °C, the developed calculation technique and software algorithm in the MatLab Simulink environment was used. The power loss coefficient, obtained by comparing power losses at the optimum temperature for a given hydraulic system in the conditions under consideration with the actual ones is proposed. The use of the coefficient will make it possible to reasonably select hydraulic fluids and set the values of the main pumps limit state and other hydraulic system elements, and evaluate the actual energy efficiency of the mining hydraulic excavator. Calculations have shown that the implementation of measures that ensure operation in the interval with a deviation of 10 % from the optimal temperature value for these conditions makes it possible to reduce energy losses from 3 to 12 %

Helfrich-Hurault elastic instabilities driven by geometrical frustration

The Helfrich-Hurault (HH) elastic instability is a well-known mechanism behind patterns that form as a result of strain upon liquid crystal systems with periodic ground states. In the HH model, layered structures undulate and buckle in response to local, geometric incompatibilities, in order to maintain the preferred layer spacing. Classic HH systems include cholesteric liquid crystals under electromagnetic field distortions and smectic liquid crystals under mechanical strains, where both materials are confined between rigid substrates. However, richer phenomena are observed when undulation instabilities occur in the presence of deformable interfaces and variable boundary conditions. Understanding how the HH instability is affected by deformable surfaces is imperative for applying the instability to a broader range of materials. In this review, we re-examine the HH instability and give special focus to how the boundary conditions influence the mechanical response of lamellar systems to geometrical frustration. We use lamellar liquid crystals confined within a spherical shell geometry as our model system. Made possible by the relatively recent advances in microfluidics within the past 15 years, liquid crystal shells are composed entirely of fluid interfaces and have boundary conditions that can be dynamically controlled at will. We examine past and recent work that exemplifies how topological constraints, molecular anchoring conditions, and boundary curvature can trigger the HH instability in liquid crystals with periodic ground states. We then end by identifying similar phenomena across a wide variety of materials, both biological and synthetic. With this review, we aim to highlight that the HH instability is a generic and often overlooked response of periodic materials to geometrical frustration

Impacts of a Supersonic Shock Front on Star Formation in the Bullet Cluster

We use the Bullet Cluster (1E0657-56) to investigate the extent to which star formation in cluster galaxies is influenced by ram pressure from supersonic gas (Mach 3) during a cluster merger. While the effects of ram pressure have been studied for individual galaxies infalling into galaxy clusters, this system provides a unique opportunity to investigate the impact of dramatic merger events on the cluster galaxy population. In this analysis we use {\it Spitzer} IRAC data to study star formation. At the redshift of the cluster the 6.2 $\mu$m PAH feature is redshifted into the 8 $\mu$m band, enabling use of the m$_{4.5}$-m$_{8}$ color as a proxy for specific star formation rate. We find that the color distribution on the two sides of the shock differ by less than 2$\sigma$, and conclude that ram pressure from the shock front has no dramatic, immediate impact on the star formation of cluster galaxies in the Bullet Cluster.Comment: 10 pages, 4 figures, Accepted for publication in Ap