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1. Circulation In Insect Wings

   https://doi.org/10.1093/icb/icaa124  

   Salcedo, MK; Socha, JJ (September 2020, Integrative and comparative biology)

   Insect wings are living, flexible structures composed of tubular veins and thin wing membrane. Wing veins can contain hemolymph (insect blood), tracheae, and nerves. Continuous flow of hemolymph within insect wings ensures that sensory hairs, structural elements such as resilin, and other living tissue within the wings remains functional. While it is well known that hemolymph circulates through insect wings, the extent of wing circulation (e.g., whether flow is present in every vein, and whether it is confined to the veins alone) is not well understood, especially for wings with complex wing venation. Over the last 100 years, scientists have developed experimental methods including microscopy, fluorescence, and thermography to observe flow in the wings. Recognizing and evaluating the importance of hemolymph movement in insect wings is critical in evaluating how the wings function both as flight appendages, as active sensors, and as thermoregulatory organs. In this review, we discuss the history of circulation in wings, past and present experimental techniques for measuring hemolymph, and broad implications for the field of hemodynamics in insect wings. 

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2. Modeling Pressure‐Dependent Wave and Vessel Compliance in the Brain Following Middle Cerebral Artery Occlusion

   https://doi.org/10.1111/micc.70049  

   Zhao, Erin; Barber, Jared; Mathew‐Steiner, Shomita S; Khanna, Savita; Sen, Chandan K; Arciero, Julia (January 2026, Microcirculation)

   ABSTRACT ObjectiveThis study demonstrates the impact of alterations in pressure, vascular compliance, arterial pulsatility, and autoregulation on tissue perfusion following middle cerebral artery (MCA) occlusion using mathematical modeling. MethodsOur previous mathematical model of the cerebral circulation is expanded to include vessel compliance and pulsatility of blood flow. An experimentally‐obtained pressure waveform is used as an incoming boundary condition to simulate the effects of vascular compliance and pulsatility of flow on perfusion following MCA occlusion. The waveform is adjusted to model the effects of elevated mean arterial pressure. ResultsIncreased distensibility reduces the amplitude of oscillations in the time‐dependent pressure solutions, whereas decreased distensibility produces more variation in these pressures. Occlusion significantly alters the magnitude of flow changes when incoming pressure is varied. The addition of the pulsatile pressure boundary condition and capacitances in the arteries and veins shifts the autoregulation plateau to higher pressures. ConclusionsThis study reveals how changes in incoming pressure affect compensatory responses to ischemic stroke caused by MCA occlusion. Boundary conditions corresponding to elevated mean arterial pressures are associated with lower degrees of ischemia, an improvement that is supported by changes in autoregulation patterns following occlusion. The results also demonstrate how increases in arterial stiffness associated with aging can inhibit the ability of the vasculature to accommodate pulsatile flow by analyzing resulting patterns such as larger amplitudes of pressure and flow oscillations in the microcirculation. The study provides a foundation for modeling the relationships among vessel compliance, arterial blood pressure, and cerebrovascular conditions. 

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3. San Albino, Nicaragua: A low-angle, thrust-controlled orogenic gold deposit

   https://doi.org/10.5382/econgeo.5042  

   Lipson, Rael_D; Goldfarb, Richard_J; Frieman, Ben_M; Payne, John (March 2024, Economic Geology)

   Abstract The San Albino deposit is an orogenic gold occurrence hosted by a low-angle thrust that is the site of a new open-pit mine in northern Nicaragua. The deposit is hosted in greenschist facies rocks of the Jurassic metasedimentary Neuvo Segovia Formation. The schist was uplifted and exposed during arc accretion and Cretaceous thin-skin deformation, forming the NE-striking Colon fold-and-thrust belt. Deformation included emplacement of the 119 to 113 Ma NE-trending Dipilto batholith into the regionally metamorphosed clastic rocks about 5 km northwest of the San Albino deposit. Mineralization is dominated by three laminated quartz vein systems (i.e., San Albino, Naranjo, Arras) that broadly follow shallowly dipping (approx. 30°) carbonaceous shears roughly concordant to schistosity along the limbs of a doubly plunging antiform. The three main parallel shears are each separated by about 90 m and individually reach a maximum thickness of about 8 m. Maximum thickness of ore zones is where post-ore local folding and reverse motion along the shallow shears has duplicated the laminated low-angle gold-bearing veins (D2 and early D3). Additional gold was added to the veins, with abundant sulfides, during a subsequent brecciation event of the early formed quartz veins that accompanied progressive thrusting (late D3). This predated boudinage of the veins during continued compression and thrust loading (D4); high gold grades are particularly notable along pyrite- and arsenopyrite-bearing stylolites formed during D4 pressure solution. The D2 to D3 gold event is likely coeval with Albian uplift of the Dipilto batholith and with back thrusting in the schist aided by the stress inhomogeneities provided by the igneous complex. Low-angle thrust-controlled orogenic gold deposits may represent world-class exploration targets because of their large linear footprints, although they are traditionally looked at as less favorable exploration targets relative to gold systems developed more commonly along high-angle reverse faults. Our case study of the San Albino deposit shows that although low-angle deposits are not inherently misoriented for failure like the more common subvertical reverse fault-related deposits, they may be sites of significant pressure buildup due to hydrothermal mineral precipitation during initial water-rock interaction or slight temperature decreases along the low-angle flow path. Resulting fluid cycling may lead to thick laminated vein development, such as seen at San Albino, where especially high-grade zones may be associated with local steepening and/or dilational zones within the broader, low-angle vein-hosting shear system. 

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4. Agreement of rebound and applanation tonometry intraocular pressure measurements during atmospheric pressure change

   https://doi.org/10.1371/journal.pone.0259143  

   Vercellin, Alice Verticchio; Harris, Alon; Siesky, Brent; Zukerman, Ryan; Tanga, Lucia; Carnevale, Carmela; Scarinci, Fabio; Oddone, Francesco (October 2021, PLOS ONE)

   Grzybowski, Andrzej (Ed.)

   This study investigated the agreement of intraocular pressure measurements using rebound tonometry and applanation tonometry in response to atmospheric changes in a hyperbaric chamber. Twelve eyes of 12 healthy subjects were included in this prospective, comparative, single-masked study. Intraocular pressure measurements were performed by rebound tonometry followed by applanation tonometry in a multiplace hyperbaric chamber at 1 Bar, followed by 2, 3 and 4 Bar during compression and again at 3 and 2 Bar during decompression. Mean differences between rebound and applanation intraocular pressure measurements were 1.6, 1.7, and 2.1 mmHg at 2, 3, and 4 Bar respectively during compression and 2.6 and 2.2 mmHg at 3 and 2 Bar during decompression. Lower limits of agreement ranged from -3.7 to -5.9 mmHg and upper limits ranged from -0.3 to 1.9 mmHg. Multivariate analysis showed that the differences between rebound and applanation intraocular pressure measurements were independent of atmospheric pressure changes (p = 0.79). Intraocular pressure measured by rebound tonometry shows a systematic difference compared to intraocular measured by applanation tonometry, but this difference is not influenced by changes of atmospheric pressure up to 4 Bar in a hyperbaric chamber. Agreement in magnitude of change between devices suggests rebound tonometry is viable for assessing intraocular pressure during atmospheric changes. Future studies should be designed in consideration of expected differences in IOP values provided by the two devices. 

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5. Lithogeochemical Vectors and Mineral Paragenesis of Hydrothermal REE-Bearing Fluorite Veins and Breccia Deposits in the Gallinas Mountains, New Mexico

   Owen, E.; Gysi, A.P.; McLemore, V. (September 2021, SEG 100)

   The Gallinas Mountains district located in Lincoln and Torrance Counties, New Mexico, is host to hydrothermal REE-bearing fluorite veins and breccia deposits. The rare earth elements (REE) are found in bastnäsite-(Ce) ([La,Ce]CO3F) which is also the primary ore mineral mined in several important carbonatite deposits (e.g. Mountain Pass in California; Bayan Obo in China). Minor production of REE, fluorite, Cu, Pb, Zn, Ag, and Fe has been recorded in the Gallinas Mountains district between the early 1900s and the 1950s. The REE-bearing fluorite veins and breccias are hosted in Permian sedimentary rocks as well as genetically related trachyte/syenite sills and dikes emplaced between 28-30 Ma. Previous studies have described the REE occurrences in the Gallinas Mountains but the controls of hydrothermal processes on the transport and deposition of REE in the district remain unclear. In this study, we combine microtextural observations with mineral and bulk rock chemistry of hydrothermal REE-bearing fluorite veins and breccias to determine the vein types, alteration styles and establish a detailed mineral paragenesis. The goal of this study is to determine lithogeochemical vectors towards REE enriched zones in the district by linking thin section and deposit scale observations with mineral and bulk rock geochemistry. This district is an exceptional natural laboratory for studying the role of hydrothermal processes for transport/deposition of REE in an alkaline F-rich magmatic- hydrothermal system because very few deposits worldwide have such well-preserved and exposed geology. Hand samples of hydrothermal veins and breccias containing fluorite ± calcite ± barite ± bastnäsite-(Ce) were collected from outcrops, prospect pits, and mine dumps. Optical microscopy was used to identify minerals and determine the textural features and crosscutting relationships of the different fluorite veins. The veins were classified into: i) hematite-fluorite veins; ii) barite- bearing bastnäsite-fluorite veins; iii) barite-bearing (fluorite)-calcite veins. Nearly all of the barite crystals in the fluorite veins display dissolution textures (skeletonized crystals) with infilling of mostly fluorite and minor calcite, suggesting that barite is part of an earlier paragenetic mineral assemblage. Bastnäsite-(Ce) is commonly found in veins containing barite and occurs either as disseminated crystals in the fluorite veins or together with fluorite infills around large barite crystals. A few of the barren fluorite-calcite veins display an intergrowth with euhedral barite crystals indicating that these could be part of an earlier barite paragenesis. These textural observations suggest a key control of REE mineralization in the Gallinas Mountains district by a coupled dissolution of barite-bearing (fluorite)-calcite veins and precipitation of later bastnäsite- fluorite veins. Geochemical bulk rock data collected from the New Mexico Bureau of Geology and Mineral Resources database were analyzed using the IMDEX ioGASTM program to definegeochemical signatures of rock types, alteration styles, and vein types. Preliminary data analysis indicates a positive correlation between Ba, F, and total rare earth oxides (TREO). These trends corroborate with the observed vein microtextures, suggesting that the interaction of a hydrothermal fluids with the barite-bearing (fluorite)-calcite veins represents a key process for defining geochemical vectors in the district. 

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