Cationic gold complexes in which gold is bound to a formally divalent carbon atom, typically formulated as gold carbenes or α-metallocarbenium ions, have been widely invoked in a range of ...gold-catalyzed transformations, most notably in the gold-catalyzed cycloisomerization of 1,
n
-enynes. Although the existence of gold carbene complexes as intermediates in gold-catalyzed transformations is supported by a wealth of indirect experimental data and by computation, until recently no examples of cationic gold carbenes/α-metallocarbenium ions had been synthesized nor had any cationic intermediates generated
via
gold-catalyzed enyne cycloaddition been directly observed. Largely for this reason, there has been considerable debate regarding the electronic structure of these cationic complexes, in particular the relative contributions of the carbene (LAu
+
&z.dbd;CR
2
) and α-metallocarbenium (LAu-CR
2
+
) forms, which is intimately related to the extent of d → p backbonding from gold to the C1 carbon atom. However, over the past ∼ seven years, a number of cationic gold carbene complexes have been synthesized in solution and generated in the gas phase and cationic intermediates have been directly observed in the gold-catalyzed cycloaddition of enynes. Together, these advances provide insight into the nature and electronic structure of gold carbene/α-metallocarbenium complexes and the cationic intermediates generated
via
gold-catalyzed enyne cycloaddition. Herein we review recent advances in this area.
This review highlights recent advances made in the synthesis of cationic gold carbene complexes and in the direct detection of cationic intermediates generated
via
gold-catalysed enyne cycloaddition.
Aerosol Jet Printing (AJP) is an emerging contactless direct write approach aimed at the production of fine features on a wide range of substrates. Originally developed for the manufacture of ...electronic circuitry, the technology has been explored for a range of applications, including, active and passive electronic components, actuators, sensors, as well as a variety of selective chemical and biological responses. Freeform deposition, coupled with a relatively large stand-off distance, is enabling researchers to produce devices with increased geometric complexity compared to conventional manufacturing or more commonly used direct write approaches. Wide material compatibility, high resolution and independence of orientation have provided novelty in a number of applications when AJP is conducted as a digitally driven approach for integrated manufacture. This overview of the technology will summarise the underlying principles of AJP, review applications of the technology and discuss the hurdles to more widespread industry adoption. Finally, this paper will hypothesise where gains may be realised through this assistive manufacturing process.
A molecular dynamics study is done on cuboid and spherical Fe
3
O
4
magnetic nanoparticles (NPs) to investigate qualitatively the influence of the molecules NH
4
OH and NaOH on their binding energy. ...This is done to determine the stability and therefore likely shape (morphology) and size of the synthesized NPs when these molecules are used as stabilizing agents. We show through molecular dynamics (MD) that small, spherical NPs synthesized with NH
4
OH, and large, cuboid NPs synthesized with NaOH, are the most stable NP systems and therefore the most likely outcome of a synthesis experiment. Furthermore, we synthesize these systems under similar conditions as predicted and find that when NaOH is used large (29 ± 2 nm), cuboid NPs are formed and when NH
4
OH is used, small (11 nm ± 2 nm), spherical NPs are formed. The role of pH is further investigated using the desorbed (and unadsorbed hydroxyl groups) as indicators of pH. The magnetic NPs are then synthesized via the co-precipitation method and the resulting NPs characterized for crystallinity, morphology, size and magnetic properties.
While the idea that adding pyrogenic carbon (referred to as ‘biochar’ when used as a soil amendment) will enhance soil fertility and carbon sequestration has gained widespread attention, ...understanding of its chemical and physical characteristics and the methods most appropriate to determine them have lagged behind. This type of information is needed to optimize the properties of biochar for specific purposes such as nutrient retention, pH amelioration or contaminant remediation. A number of surface properties of a range of biochar types were examined to better understand how these properties were related to biochar production conditions, as well as to each other. Among biochars made from oak (
Quercus lobata), pine (
Pinus taeda) and grass (
Tripsacum floridanum) at 250
°C in air and 400 and 650
°C under N
2, micropore surface area (measured by CO
2 sorptometry) increased with production temperature as volatile matter (VM) decreased, indicating that VM was released from pore-infillings. The CEC, determined using K
+ exchange, was about 10
cmol
c
kg
−1 for 400 and 650
°C chars and did not show any pH dependency, whereas 250
°C biochar CECs were pH-dependant and rose to as much as 70
cmol
c
kg
−1 at pH 7. Measurements of surface charge on biochar particles indicated a zeta potential of −
9 to −
4
mV at neutral pH and an iso-electric point of pH 2–3. However, a colloidal or dissolved biochar component was 4–5 times more electronegative. Total acid functional group concentration ranged 4.4–8.1
mmol
g
−1 (measured by Boehm titration), decreased with production temperature, and was directly related to VM content. Together, these findings suggest that the VM component of biochar carries its acidity, negative charge, and thus, complexation ability. However, not all acid functional groups exchanged cations as the number of cation exchanging sites (CEC) was about 10 times less than the number of acid functional groups present on biochar surfaces and varied with biomass type. These findings suggest that lower temperature biochars will be better used to increase soil CEC while high temperature biochars will raise soil pH. Although no anion exchange capacity was measured in the biochars, they may sorb phosphate and nitrate by divalent cation bridging.
► Biochar surface area mainly in micropores and best measured by CO
2 sorptometry. ► The volatile component of biochar generates biochar acidity and CEC. ► Biochar surface is negatively charged. ► High temperature chars increase soil pH and low temperature chars increase CEC.
The interaction of a PEGylated and non-PEGylated Fe
3
O
4
nanoparticle drug-delivery system, with 5-fluorouracil (5-FU) as the chemotherapy drug, is investigated via atomistic molecular dynamics ...(MD). The induced pore formation in a dipalmitoylphosphatidylcholine (DPPC) bilayer phospholipid (BLPL) is studied, and the resulting hourglass-shaped pores with hydrophilic lipid headgroups lining the pores are observed. Furthermore, we optimize the required number of ligands that are required to allow for the formed pores to spontaneously reseal. Additionally, the number of water molecules that transverse through the water bridge is investigated. These results may be useful to design nanocarrier systems that will maintain the cellular osmotic pressure and stability, while the 5-FU is converted to the required metabolites inside the cell to serve its purpose as a chemotherapeutic drug.
The transport of carbon into Earth's mantle is a critical pathway in Earth's carbon cycle, affecting both the climate and the redox conditions of the surface and mantle. The largest unconstrained ...variables in this cycle are the depths to which carbon in sediments and altered oceanic crust can be subducted and the relative contributions of these reservoirs to the sequestration of carbon in the deep mantle
. Mineral inclusions in sublithospheric, or 'superdeep', diamonds (derived from depths greater than 250 kilometres) can be used to constrain these variables. Here we present oxygen isotope measurements of mineral inclusions within diamonds from Kankan, Guinea that are derived from depths extending from the lithosphere to the lower mantle (greater than 660 kilometres). These data, combined with the carbon and nitrogen isotope contents of the diamonds, indicate that carbonated igneous oceanic crust, not sediment, is the primary carbon-bearing reservoir in slabs subducted to deep-lithospheric and transition-zone depths (less than 660 kilometres). Within this depth regime, sublithospheric inclusions are distinctly enriched in
O relative to eclogitic lithospheric inclusions derived from crustal protoliths. The increased
O content of these sublithospheric inclusions results from their crystallization from melts of carbonate-rich subducted oceanic crust. In contrast, lower-mantle mineral inclusions and their host diamonds (deeper than 660 kilometres) have a narrow range of isotopic values that are typical of mantle that has experienced little or no crustal interaction. Because carbon is hosted in metals, rather than in diamond, in the reduced, volatile-poor lower mantle
, carbon must be mobilized and concentrated to form lower-mantle diamonds. Our data support a model in which the hydration of the uppermost lower mantle by subducted oceanic lithosphere destabilizes carbon-bearing metals to form diamond, without disturbing the ambient-mantle stable-isotope signatures. This transition from carbonate slab melting in the transition zone to slab dehydration in the lower mantle supports a lower-mantle barrier for carbon subduction.
High quality coastal aquifer systems provide vast quantities of potable groundwater for millions of people worldwide. Managing this setting has economic and environmental consequences. Specific ...knowledge of the dynamic relationship between fresh terrestrial groundwater discharging to the ocean and seawater intrusion is necessary. We present multi- disciplinary research that assesses the relationships between groundwater throughflow and seawater intrusion. This combines numerical simulation, geophysics, and analysis of more than 30 years of data from a seawater intrusion monitoring site. The monitoring wells are set in a shallow karstic aquifer system located along the southwest coast of Western Australia, where hundreds of gigalitres of fresh groundwater flow into the ocean annually. There is clear evidence for seawater intrusion along this coastal margin. We demonstrate how hydraulic anisotropy will impact on the landward extent of seawater for a given groundwater throughflow. Our examples show how the distance between the ocean and the seawater interface toe can shrink by over 100% after increasing the rotation angle of hydraulic conductivity anisotropy when compared to a homogeneous aquifer. We observe extreme variability in the properties of the shallow aquifer from ground penetrating radar, hand samples, and hydraulic parameters estimated from field measurements. This motived us to complete numerical experiments with sets of spatially correlated random hydraulic conductivity fields, representative of karstic aquifers. The hydraulic conductivity proximal to the zone of submarine groundwater discharge is shown to be significant in determining the overall geometry and landward extent of the seawater interface. Electrical resistivity imaging (ERI) data was acquired and assessed for its ability to recover the seawater interface. Imaging outcomes from field ERI data are compared with simulated ERI outcomes derived from transport modelling with a range of hydraulic conductivity distributions. This process allows for interpretation of the approximate geometry of the seawater interface, however recovery of an accurate resistivity distribution across the wedge and mixing zone remains challenging. We reveal extremes in groundwater velocity, particularly where fresh terrestrial groundwater discharges to the ocean, and across the seawater recirculation cell. An overarching conclusion is that conventional seawater intrusion monitoring wells may not be suitable to constrain numerical simulation of the seawater intrusion. Based on these lessons, we present future options for groundwater monitoring that are specifically designed to quantify the distribution of; (i) high vertical and horizontal pressure gradients, (ii) sharp variations in subsurface flow velocity, (iii) extremes in hydraulic properties, and (iv) rapid changes in groundwater chemistry. These extremes in parameter distribution are common in karstic aquifer systems at the transition from land to ocean. Our research provides new insights into the behaviour of groundwater in dynamic, densely populated, and ecologically sensitive coastal environments found worldwide.
Neuroimmune signaling in alcohol use disorder Erickson, Emma K.; Grantham, Emily K.; Warden, Anna S. ...
Pharmacology, biochemistry and behavior,
02/2019, Letnik:
177
Journal Article
Recenzirano
Odprti dostop
Alcohol use disorder (AUD) is a widespread disease with limited treatment options. Targeting the neuroimmune system is a new avenue for developing or repurposing effective pharmacotherapies. Alcohol ...modulates innate immune signaling in different cell types in the brain by altering gene expression and the molecular pathways that regulate neuroinflammation. Chronic alcohol abuse may cause an imbalance in neuroimmune function, resulting in prolonged perturbations in brain function. Likewise, manipulating the neuroimmune system may change alcohol-related behaviors. Psychiatric disorders that are comorbid with AUD, such as post-traumatic stress disorder, major depressive disorder, and other substance use disorders, may also have underlying neuroimmune mechanisms; current evidence suggests that convergent immune pathways may be involved in AUD and in these comorbid disorders. In this review, we provide an overview of major neuroimmune cell-types and pathways involved in mediating alcohol behaviors, discuss potential mechanisms of alcohol-induced neuroimmune activation, and present recent clinical evidence for candidate immune-related drugs to treat AUD.
•Alcohol exposure perturbs innate immune signaling in brain.•A wide array of neuroimmune molecules regulate behavioral responses to alcohol.•Microglia and astrocyte dysfunction may contribute to addictive behaviors.•Neuroimmune imbalance may confer vulnerability to psychiatric disorders.•Immunomodulatory drugs are new candidates for treating alcohol use disorder.
Obtaining high-quality measurements close to a large earthquake is not easy: one has to be in the right place at the right time with the right instruments. Such a convergence happened, for the first ...time, when the 28 September 2004 Parkfield, California, earthquake occurred on the San Andreas fault in the middle of a dense network of instruments designed to record it. The resulting data reveal aspects of the earthquake process never before seen. Here we show what these data, when combined with data from earlier Parkfield earthquakes, tell us about earthquake physics and earthquake prediction. The 2004 Parkfield earthquake, with its lack of obvious precursors, demonstrates that reliable short-term earthquake prediction still is not achievable. To reduce the societal impact of earthquakes now, we should focus on developing the next generation of models that can provide better predictions of the strength and location of damaging ground shaking.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Resolution of inflammation is an active and dynamic process after surgery. Maresin 1 (MaR1) is one of a growing number of specialised pro-resolving lipids biosynthesised by macrophages that regulates ...acute inflammation. We investigated the effects of MaR1 on postoperative neuroinflammation, macrophage activity, and cognitive function in mice.
Adult male C57BL/6 (n=111) and Ccr2RFP/+Cx3cr1GFP/+ (n=54) mice were treated with MaR1 before undergoing anaesthesia and orthopaedic surgery. Systemic inflammatory changes, bone healing, neuroinflammation, and cognition were assessed at different time points. MaR1 protective effects were also evaluated using bone marrow derived macrophage cultures.
MaR1 exerted potent systemic anti-inflammatory effects without impairing fracture healing. Prophylaxis with MaR1 prevented surgery-induced glial activation and opening of the blood–brain barrier. In Ccr2RFP/+Cx3cr1GFP/+ mice, fewer infiltrating macrophages were detected in the hippocampus after surgery with MaR1 prophylaxis, which resulted in improved memory function. MaR1 treatment also reduced expression of pro-inflammatory cell surface markers and cytokines by in vitro cultured macrophages. MaR1 was detectable in the cerebrospinal fluid of older adults before and after surgery.
MaR1 exerts distinct anti-inflammatory and pro-resolving effects through regulation of macrophage infiltration, NF-κB signalling, and cytokine release after surgery. Future studies on the use of pro-resolving lipid mediators may inform novel approaches to treat neuroinflammation and postoperative neurocognitive disorders.
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