Heating Protocol Research Articles

Independent and Cumulative Effects of Superoxide and iNOS on Cutaneous NO‐Dependent Vasodilation in Normotensive Non‐Hispanic Blacks and Whites

Cardiovascular disease is the foremost cause of morbidity and mortality in non-Hispanic Blacks (NHB). This may be due, in part, to reduced microvascular endothelial nitric oxide (NO) bioavailability and increased oxidative stress. The purpose of this study was to investigate the role of iNOS and superoxide, individually and cumulatively, in the cutaneous microvascular response to local heating in normotensive NHB and non-Hispanic Whites (NHW). Participants (n = 6 per group) were instrumented with four microdialysis fibers 1) lactated Ringer's solution (control), 2) 0.1 mM 1400W iNOS inhibitor, 3) 10 μM tempol, a superoxide dismutase mimetic to scavenge superoxide, and 4) combined 1400W + tempol. Following perfusate infusion, local skin temperature was increased via rapid local heating to 39°C (0.1°C s-1). Once skin blood flow plateaued, 20 mM L-NAME was infused to quantify endothelial NOS-dependent vasodilation to the local heating response. Following L-NAME infusion, the local heaters were increased to 43°C and 54mM of sodium nitroprusside was infused to elicit maximal cutaneous vasodilation. Skin blood flow was measured via laser-doppler flowmetry (LDF) throughout the local heating protocol. Percent NO contribution (%NO) was calculated as the difference between the local heating plateau and the post-L-NAME plateau multiplied by 100. Data are means ± SD. The %NO contribution was reduced at control sites in NHB relative to NHW (46 ± 5 vs. 62 ± 10 %NO, p = 0.03). Each experimental site was significantly different compared to control in NHB participants [(1400W, 63 ± 7 %NO, p = 0.01); (tempol, 61 ± 8 %NO, p = 0.01); (combined, 77 ± 9 %NO, p < 0.01)]. There was no effect of any of the treatments on %NO in NHW participants. Percent NO contribution at the combined site in NHB was significantly higher compared to control in NHW (p = 0.02). These data indicate combined superoxide scavenging and iNOS inhibition can increase endothelial NO-dependent cutaneous vasodilation more than either treatment alone in NHB.

Women with a History of Preeclampsia Have Preserved Neurogenically‐Mediated Dilation in the Cutaneous Microvasculature

Women who have had preeclampsia (PrEC) demonstrate microvascular endothelial dysfunction, mediated in part by reduced nitric oxide (NO)-dependent mechanisms. Localized heating of the skin induces a biphasic vasodilation response: a neurogenically-mediated initial peak, followed by a sustained endothelium-dependent plateau. We have previously shown that the endothelium-dependent plateau is attenuated in PrEC, due to attenuated NO-dependent dilation. However, it is unknown if the same is true concerning the neurogenically-mediated initial peak. The purpose of this study was to (1) examine the effect of preeclampsia history on neurogenically-mediated vasodilation and the NO-dependent contribution to that response, and (2) examine the relation between NO-dependent neurogenic dilation and the NO-dependent portion of the endothelium-dependent plateau. We hypothesized that PrEC would have an attenuated initial peak response and a reduced NO-dependent contribution to that response compared to women with a history of normotensive pregnancy (HC). Six HC (31±2yrs, 7±2 months post-partum) and 7 PrEC (29±2yrs, 7±3months post-partum) underwent a standard local heating protocol (42°C; 0.1°C·s-1). Two intradermal microdialysis fibers were placed in the skin of the ventral forearm for the continuous local delivery of Lactated Ringer's alone (control) or 15mM NG-nitro-L-arginine methyl ester (L-NAME) for nitric oxide synthase (NOS)-inhibition. Red blood cell flux was measured at each site via laser-Doppler flowmetry (LDF). Cutaneous vascular conductance was calculated (CVC=LDF/mean arterial pressure) and normalized to maximum (%CVCmax; 28mM SNP + local heat 43°C). NO-dependent dilation was calculated within-subject as the difference between control and NOS-inhibited sites. There were no differences in the initial peak between groups (HC: 80±5 vs PrEC: 79±5 %CVCmax; p=.88). NOS-inhibition attenuated the initial peak in both HC (Control: 80±5 vs L-NAME: 57±9 %CVCmax; p=0.02) and PrEC (Control: 79±5 vs L-NAME: 53±6 %CVCmax; p=0.004). However, there were no group differences in the NO-dependent portion of initial peak (HC: 23±8 vs PrEC: 24±5 %CVCmax; p=0.97). The local heating plateau (HC: 99±2 vs PrEC: 85±1 %CVCmax; p<0.001) and NO-contribution to the plateau (HC: 47±5 vs PrEC: 14±5 %CVCmax; p<0.001) were attenuated in PrEC compared to HC. There was no relation between NO-dependent dilation in the initial peak and NO-dependent dilation in the plateau across groups (R2 = 0.05; p = 0.51). Women who have had preeclampsia demonstrate attenuated microvascular endothelium-dependent dilation compared to women with a history of uncomplicated pregnancy. However, there are no differences in neurogenically-mediated vasodilation between the groups, suggesting that the NO-dependent vasodilation of the neurogenic response is not related to endothelium-dependent NO-mediated dilation in these women.

Computational modeling of the effect of blood flow and dual phase lag on tissue temperature during tumor treatment by magnetic hyperthermia

This paper is devoted to the development of a mathematical model and its computational analysis targeted at investigating the effects of dual-phase lag on the heating protocol of tumor tissue by the method of electromagnetic hyperthermia. The model comprises two layers, one of them being the vessel layer in which blood flows under the action of a pressure gradient and an external magnetic field, while the other is a tissue layer containing a small rectangular tumor. The tumor tissue is heated by the periodic nature of metabolic and external heat sources. Two phase lags due to the presence of temperature gradient and heat flux are treated to observe the effect of faster heating phenomena. The wave equation representing bioheat transfer in the tissue layer is considered. The problem has been solved directly by employing a suitable finite difference numerical tool. The study shows that the phase lag caused by heat flux is more effective for heating the tumor than the phase lag due to the temperature gradient, and further that transversely applied magnetic field to the blood flow has a limited impact on enhancing the tumor temperature.

On the estimation of marbles weathering by thermal action using drilling resistance

Marbles are widely present in noteworthy constructions but are prone to decay due to the anisotropic thermal behavior of constituent minerals. In this paper, fine to coarse sound marbles possessing diverse technical properties were subjected to different artificial heating protocols to simulate varied degradation scenarios. The ultrasonic pulse velocity of sound and decayed marbles decreases exponentially with increasing porosity which is in line with the relationships found in the literature for other marble varieties. Drilling resistance (DR) revealed potential to characterize a wide diversity of marbles/degradation levels since data was in straight agreement with technical properties of interest for damage diagnosis and conservation purposes. Therefore, empirical relations based on DR results are provided to estimate technical properties of marbles on-site. Besides, this work proposes a classification, based on DR, to assess the weathering level of marbles.

Effect of sintering process on microstructure, 4-point flexural strength, and grain size of yttria-stabilized tetragonal zirconia polycrystal for use in monolithic dental restorations

Statement of problemModifications have been made in the microstructure and sintering parameters of monolithic zirconia to improve esthetics qualities and avoid chipping of 2-layer restorations. However, how these modifications affect the physical and mechanical properties of zirconia is unclear. PurposeThe purpose of this in vitro study was to compare the influence of different sintering parameters on the microstructure, 4-point flexural strength, density, and grain size of 2 commercially available zirconia advocated for the fabrication of monolithic dental prostheses and 1 commercially available zirconia for use as a core material. Material and methodsThree presintered blocks (Ceramill Zolid, Prettau, and IPS e.max ZirCAD) were used. Specimens were cut and sintered as per the manufacturer's recommendation or as per a modified heating protocol. Ceramill Zolid (Z1450) was sintered at 1450 °C, Prettau (P1600) was sintered at 1600 °C, and IPS e.max ZirCAD (I1530) was sintered at 1530 °C by following the manufacturer's heating protocol. Groups Ceramill Zolid Z1530 and Z1600 were sintered at temperatures higher than the manufacturer's recommendation. Specimens from each group (n=13) were analyzed with X-ray diffraction (XRD), density calculus, average grain size measurement, and 4-point flexural tests. Data were compared by using ANOVA (α=.05). ResultsXRD analysis showed the presence of a tetragonal metastable phase in all groups before and after sintering. No significant differences were found in relative density values for the 3 Ceramill groups (5.98 g/cm3). Groups I1530 (6.03 g/cm3) and P1600 (6.03 g/cm3) had similar density results greater than 6.00 g/cm3. The average grain size of all groups remained lower than 1 μm. P1600 had the highest grain size (0.817 μm), and Z1450 presented the lowest grain size (0.465 μm). P1600 showed the most homogeneous flexural strength and the highest Weibull modulus (m=8.22). Z1530 presented the lowest Weibull modulus (m=4.58). IPS e.max ZirCAD (I1530) had the highest flexural strength (1057.41 ±150.54 MPa), and Ceramill Zolid Z1450 had the lowest (621.01 ±138.08 MPa). ConclusionsThe flexural strength, microstructure, crystal phase, and grain size of the analyzed zirconia varied as per the sintering processing. The IPS e.max ZirCAD had the highest flexural strength (1057.41 ±150.54 MPa), followed by Prettau zirconia (864.18 ±118.21), with a statistically significant difference (P<.05). The Ceramill Zolid zirconia presented the lowest flexural strength, as well as the lowest reliability for all sintering parameters used (Z1450: 621.01 ±138.08 MPa and m=5.42; Z1530: 713.10 ±175.44 MPa and m=4.58; Z1600: 630.15 ±112.08 MPa and m=6.87). At a lower heating rate (8 °C/min), the final density increased and excessive grain growth in group Z1530 was prevented.

Microstructures of Ti6Al4V matrices induce structural evolution of bioactive surface oxide layers via cold compression and induction heating

Considerable efforts have been devoted to the construction of micro- and nanostructured surfaces to improve the clinical application of Ti-based orthopedic implants. However, the preparation of bioactive microstructures with tunable characteristics remains challenging. Herein, we investigated the structural evolution of oxide layers on Ti6Al4V surfaces by conducting a cold compression and induction heating protocol. We found that the properties of the metallographic microstructures determined the size and structure of oxide crystallites formed via a seeding mechanism: the finer the matrix grains, the smaller the oxide crystallites. In addition, the alloy matrix grain sizes steadily increased with increasing axial compression because of recrystallization during induction heating. The formation of nanoscale rutile (TiO2) crystallites caused an increase of surface roughness and hardness, and considerably improved the bioactivity of Ti6Al4V, as measured by the degree of hydroxyapatite deposition in simulated body fluid in vitro. However, oversized oxide crystallites had a negative effect on the promotion of hydroxyapatite deposition. This important finding offers a feasible method for the controllable in-situ construction of bioactive oxide layers by designing the required matrix microstructures of Ti-based implant materials.

Effects of alternatively used thermal treatments on the mechanical and fracture behavior of dental resin composites with varying filler content

The purpose of this study was two-fold: (i) to investigate whether the thermal treatment of direct dental resin composites (RCs) using microwave or autoclave heating cycles would modify the materials' strength as compared to the protocol without heating (control); and (ii) to compare the mechanical performance of direct and indirect RCs. Three RCs (from 3M ESPE) were tested: one indirect (Sinfony); and two direct materials (microhybrid – Filtek Z250; and nanofilled – Filtek Z350). Specimens from the direct RCs were prepared and randomly allocated into three groups according to the thermal treatment (n = 10): Control – no thermal treatment was performed; Microwave – the wet heating was performed using a microwave oven; and Autoclave – the wet heating was performed in an autoclave oven. The indirect RC was prepared following the instructions of the manufacturer. All materials were tested using flexural strength, elastic modulus, work of fracture (Wf), microhardness, and scanning electron microscopy (SEM) analyses. Data were analyzed with ANOVA and Tukey as well as Weibull analysis (α = 0.05). The thermal treatments tended to produce slight changes in the topography of direct RCs, especially by the autoclave’ wet heating. Overall, the physico-mechanical properties changed after thermal treatment, although this effect was dependent on the type of RC and on the heating protocol. Sinfony showed the lowest modulus and hardness of the study, although it was the most compliant system (higher work of fracture). The load-deflection ability was also greater for the indirect RC. Reliability of the tested materials was similar among each other (p > 0.05). In conclusion, the alternative thermal treatments suggested here may significantly influence some aspects of the mechanical behavior of dental resin composites, with negative effects relying on both the chemical composition of the restorative material as well as on the wet heating protocol used. Clinicians should be aware of the possible effects that additional wet heating of direct resin composites using microwave or autoclave thermal protocols as performed here could have on the overall fracture and mechanical responses during loading circumstances.

An evaluation of inkjet printed amino acid fingerprint test targets for ninhydrin process monitoring − and some observations

Ninhydrin was implemented as the primary police method of developing latent fingermarks on paper, cardboard and some other porous surfaces from the late 1960s. Some researchers have used individual amino acids, or mixtures of amino acids, as a method of testing the effectiveness of reagent formulations. It was not however known whether simple mixtures of amino acids could effectively emulate latent fingermarks in reactions with reagents such as ninhydrin. The first part of this study compared the effects of ninhydrin fingermark treatments used internationally in various police laboratories on test targets created by inkjet printing graduated concentrations of a representative mixture of amino acids in a series of blocks on paper. Variations in intensity of development were observed between laboratories which used various formulations and heat and humidity post treatment protocols. In a further trial in 2015 several participants in the International Fingerprint Research Group (IFRG) meeting processed test targets in their own laboratories and submitted them for measurement. Again, variation in developed intensity was observed. The depletion of the activity of ninhydrin solutions during use was also investigated in early evaluations of the test targets. An established fingerprint laboratory then processed a number of samples from a batch of targets to examine batch consistency. This was followed by designing a new test target which enabled comparisons between the developed intensity of printed test target blocks alongside depletion series of split, natural donor fingermarks. A panel of 20 donors provided depletion fingermarks and four ninhydrin formulations and treatment protocols were used. The developed test target blocks were scanned, intensity of development measured, and the results compared with the fingermark development which was evaluated by three assessors using two types of scale. Good correlation between the intensity of the developed test targets and latent fingermark quality and intensity scores was observed with the four ninhydrin treatment protocols, including some which used deliberately downgraded ninhydrin concentrations. This type of evaluation was carried out a second time to investigate modified heat and humidity protocols. The use of such test targets for routine reagent quality control and process verification would appear to be far more accurate and reliable than the use of small numbers of donor fingermarks. It is not clear why the different ninhydrin formulations investigated in the latter part of the work have very different optimum post treatment heating regimes.

Heat and Humidity for Bioburden Reduction of N95 Filtering Facepiece Respirators.

Introduction: The coronavirus disease 2019 (COVID-19) pandemic has caused a global shortage of single-use N95 filtering facepiece respirators (FFRs). A combination of heat and humidity is a promising method for N95 FFR decontamination in crisis-capacity conditions; however, an understanding of its effect on viral inactivation and N95 respirator function is crucial to achieving effective decontamination. Objective: We reviewed the scientific literature on heat-based methods for decontamination of N95 FFRs contaminated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and viral analogues. We identified key parameters for SARS-CoV-2 bioburden reduction while preserving N95 fit and filtration, as well as methods that are likely ineffective. Key Findings: Viral inactivation by humid heat is highly sensitive to temperature, humidity, duration of exposure, and the local microenvironment (e.g., dried saliva). A process that achieves temperatures of 70-85°C and relative humidity >50% for at least 30 min is likely to inactivate SARS-CoV-2 (>3-log reduction) on N95 respirators while maintaining fit and filtration efficiency for three to five cycles. Dry heat is significantly less effective. Microwave-generated steam is another promising approach, although less studied, whereas 121°C autoclave treatments may damage some N95 FFRs. Humid heat will not inactivate all microorganisms, so reprocessed N95 respirators should be reused only by the original user. Conclusions: Effective bioburden reduction on N95 FFRs during the COVID-19 pandemic requires inactivation of SARS-CoV-2 and preservation of N95 fit and filtration. The literature suggests that humid heat protocols can achieve effective bioburden reduction. Proper industrial hygiene, biosafety controls, and clear protocols are required to reduce the risks of N95 reprocessing and reuse.

The CH(X2Π) + H2O reaction: two transition state kinetics.

The reaction of ground state methylidyne (CH) with water vapor (H2O) is theoretically re-investigated using high-level coupled cluster computations in combination with semi-classical transition state theory (SCTST) and two-dimensional master equation simulations. Insertion of CH into a H-O bond of H2O over a submerged barrier via a well-skipping mechanism yielding solely H and CH2O is characterized. The reaction kinetics is effectively determined by the formation of a pre-reaction van der Waals complex (PRC, HC-OH2) and its subsequent isomerization to activated CH2OH in competition with PRC re-dissociation. The tunneling effects are found to be minor, while variational effects in the PRC → CH2OH step are negligible. The calculated rate coefficient k(T) is nearly pressure-independent, but strongly depends on temperature with pronounced down-up behavior: a high value of 2 × 10-10 cm3 s-1 at 50 K, followed by a fairly steep decrease down to 8 × 10-12 cm3 s-1 at 900 K, but increasing again to 5 × 10-11 cm3 s-1 at 3500 K. Over the T-range of this work, k(T) can be expressed as: k(T, P = 0) = 2.31 × 10-11 (T/300 K)-1.615 exp(-38.45/T) cm3 s-1 for T = 50-400 K k(T, P = 0) = 1.15 × 10-12 (T/300 K)0.8637 exp(892.6/T) cm3 s-1 for T = 400-1000 K k(T, P = 0) = 4.57 × 10-15 (T/300 K)3.375 exp(3477.4/T) cm3 s-1 for T = 1000-3500 K.

Effect of intracanal and extracanal heating on pulp dissolution property of continuous chelation irrigant.

Context:Extracanal and intracanal heating of sodium hypochlorite (NaOCl) improve its pulp dissolution, but limited literature is available on its effect as a combined single irrigant with etidronate.Aim:The aim of this study is to compare the effect of temperature on the effectiveness of NaOCl and continuous chelation protocol on the time required for the dissolution of vital and necrotic pulp.Materials and Methods:Dissolution time of 120 standardized bovine (buffalo) pulp fragments, divided into 12 subgroups based on tissue type (vital/necrotic), irrigant (NaOCl/continuous chelation), and temperature (extracanal, intracanal, and nonheated irrigant), was noted. Conical glass tips mimicking the root canal were considered specimen containers. About 0.2 ml of irrigant corresponding to the irrigation protocol was taken in them and then pulp samples were added to it. Samples were observed using loupes under 2.5 X magnification. Dissolution time was recorded using a stopwatch. The study was approved by the Institutional Ethical Committee (SDC/2019/591).Statistical Analysis Used:Two-way analysis of variance; statistical product and service solutions version 25. The level of significance was set at P < 0.05.Results:Time for pulp dissolution by continuous chelation mixture was significantly more as compared to NaOCl alone in all subgroups. Pulp tissue dissolution for both vital and necrotic pulp was improved by the increase in temperature of both irrigants and dissolution time was more for necrotic than vital tissue. Pulp tissue dissolution was significantly better by intracanal heating as compared to extracanal heating.Conclusion:Although intracanal heating of continuous chelation mixture improves its pulp dissolution capacity significantly as compared to extracanal heating and nonheating protocol but pulpal dissolution capacity of nonheated 5% NaOCl still remains significantly better as compared to intracanal and extracanal heated continuous chelation mixture.

Numerical analysis of the pulsating heat source effects in a tumor tissue

Background and objectivesHyperthermia treatment is nowadays recognized as the fourth additional cancer therapy technique following surgery, chemotherapy, and radiation; it is a minimally or non-invasive technique which involves fewer complications, a shorter hospital stay, and fewer costs. In this paper, pulsating heat effects on heat transfer in a tumor tissue under hyperthermia are analyzed. The objective of the paper is to find and quantify the advantages of pulsatile heat protocols under different periodical heating schemes and for different tissue morphologies. MethodsThe tumor tissue is modeled as a porous sphere made up of a solid phase (tissue, interstitial space, etc.) and a fluid phase (blood). A Local Thermal Non-Equilibrium (LTNE) model is employed to consider the local temperature difference between the two phases. Governing equations with the appropriate boundary conditions are solved with the finite-element code COMSOL Multiphysics®. The pulsating effect is modeled with references to a cosine function with different frequencies, and such different heating protocols are compared at equal delivered energy, i. e. different heating times at equal maximum power. ResultsDifferent tissue properties in terms of blood vessels sizes and blood volume fraction in tissue (porosity) are investigated. The results are shown in terms of tissue temperature and percentage of necrotic tissue obtained. The most powerful result achieved using a pulsating heat source instead of a constant one is the decreasing of maximum temperature in any considered case, even reaching about 30% lower maximum temperatures. Furthermore, the evaluation of tissue damage at the end of treatment shows that pulsating heat allows to necrotize the same tumoral tissue area of the non-pulsating heat source. ConclusionsModeling pulsating heat protocols in thermal ablation under different periodical heating schemes and considering different tissues morphologies in a tumor tissue highlights how the application of pulsating heat sources allows to avoid high temperature peaks, and simultaneously to ablate the same tumoral area obtained with a non-pulsating heat source. This is a powerful result to improve medical protocols and devices in thermal ablation of tumors.

Association of the Thermodynamics with the Functionality of Thermoresponsive Chimeric Nanosystems.

Stimuli-responsive nanosystems are an emerging technology in the field of therapy and are very promising for various applications, including targeted drug delivery. In this chapter, our scope is to integrate two different methodologies, namely differential scanning calorimetry (DSC) and dynamic light scattering (DLS), in order to rationally approach the functional behavior of thermoresponsive chimeric/mixed liposomes and interpret their thermoresponsiveness on a thermodynamic basis. In particular, chimeric bilayers comprised of the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and two different-in-composition thermoresponsive amphiphilic block copolymers poly(N-isopropylacrylamide)-b-poly(lauryl acrylate) (PNIPAM-b-PLA) 1 or 2 were built by a conventional evaporation technique, followed by DSC, and chimeric liposomes of DPPC and PNIPAM-b-PLA 1 were developed and studied by DLS, after preparation and after a simple heating protocol. The results from both methodologies indicate the composition- and concentration-dependent lyotropic effect of the foreign copolymer molecule on the properties and functionality of the lipidic membrane.

Significance of Rarefaction, Streamwise Conduction, and Viscous Dissipation on the Extended Graetz–Nusselt Problem: The Case of Finite-Length Microchannels with Prescribed Wall Heat Flux

The article addresses the extended Graetz–Nusselt problem in finite-length microchannels for prescribed wall heat flux boundary conditions, including the effects of rarefaction, streamwise conduction, and viscous dissipation. The analytical solution proposed, valid for low-intermediate Peclet values, takes into account the presence of the thermal development region. The influence of all transport parameters (PecletPe, KnudsenKn, and BrinkmanBr) and geometrical parameters (entry length and microchannel aspect ratio) is investigated. Performances of different wall heat flux functions have been analyzed in terms of the averaged Nusselt number. In the absence of viscous dissipationBr=0, the best heating protocol is a decreasing wall heat flux function. In the presence of dissipationBr&gt;0, the best heating protocol is a uniform wall heat flux.

Heat shock protein 90 modulates cutaneous vasodilation during an exercise-heat stress, but not during passive whole-body heating in young women.

Heat shock protein 90 (HSP90) modulates exercise‐induced cutaneous vasodilation in young men via nitric oxide synthase (NOS), but only when core temperature is elevated ~1.0°C. While less is known about modulation of this heat loss response in women during exercise, sex differences may exist. Further, the mechanisms regulating cutaneous vasodilation can differ between exercise‐ and passive‐heat stress. Therefore, in 11 young women (23 ± 3 years), we evaluated whether HSP90 contributes to NOS‐dependent cutaneous vasodilation during exercise (Protocol 1) and passive heating (Protocol 2) and directly compared responses between end‐exercise and a matched core temperature elevation during passive heating. Cutaneous vascular conductance (CVC%max) was measured at four forearm skin sites continuously treated with (a) lactated Ringers solution (control), (b) 178 μM Geldanamycin (HSP90 inhibitor), (c) 10 mM L‐NAME (NOS inhibitor), or (d) combined 178 μM Geldanamycin and 10 mM L‐NAME. Participants completed both protocols during the early follicular (low hormone) phase of the menstrual cycle (0–7 days). Protocol 1: participants rested in the heat (35°C) for 70 min and then performed 50 min of moderate‐intensity cycling (~55% VO2peak) followed by 30 min of recovery. Protocol 2: participants were passively heated to increase rectal temperature by 1.0°C, comparable to end‐exercise. HSP90 inhibition attenuated CVC%max relative to control at end‐exercise (p < .05), but not during passive heating. While NOS inhibition and combined HSP90 + NOS inhibition attenuated CVC%max relative to control for both protocols (all p < .05), they did not differ from each other. We show that HSP90 modulates cutaneous vasodilation NOS‐dependently during exercise in young women, with no effect during passive heating, despite a similar NOS contribution.

Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages

SummaryBackgroundIn the wake of the SARS-CoV-2 pandemic and unprecedented global demand, clinicians are struggling to source adequate access to personal protective equipment. Respirators can be in short supply, though are necessary to protect workers from SARS-CoV-2 exposure. Rapid decontamination and reuse of respirators may provide relief for the strained procurement situation.MethodIn this study, we investigated the suitability of 70°C dry heat and microwave-generated steam (MGS) for reprocessing of FFP2/N95-type respirators, and Type-II surgical face masks. Staphylococcus aureus was used as a surrogate as it is less susceptible than enveloped viruses to chemical and physical processes.ResultsWe observed >4 log10 reductions in the viability of dry S. aureus treated by dry heat for 90 min at 70°C and >6 log10 reductions by MGS for 90 s. After 3 reprocessing cycles, neither process was found to negatively impact the bacterial or NaCl filtration efficiency of the respirators that were tested. However, MGS was incompatible with Type-II surgical masks tested, as we confirmed that bacterial filtration capacity was completely lost following reprocessing. MGS was observed to be incompatible with some respirator types due to arcing observed around some types of metal nose clips and by loss of adhesion of clips to the mask.ConclusionConsidering the advantages and disadvantages of each approach, we propose a reprocessing personal protective equipment/face mask workflow for use in medical areas.

One-pot modular synthesis of β-chalcogen amides via regioselective 2-oxazolines ring-opening reaction promoted by indium chalcogenolates under microwave irradiation

We describe herein a microwave-assisted synthesis of β-chalcogen amides through the regioselective ring-opening reaction of 2-oxazolines promoted by bis(organoylchalcogeno)iodo indium(III) in situ generated. This protocol allows the preparation of structurally diverse β-chalcogen amides, with moderate to good yields, within a much shorter reaction time compared to conventional heating protocols.

Systematics of H2 and H2O evolved from chlorites during oxidative dehydrogenation

AbstractThermally induced dehydroxylation and oxidative dehydrogenation drive the thermal decomposition of all Fe2+-containing phyllosilicates. Whereas the former produces H2O gas, the latter results in H2 evolution. Six chlorites representing the Mg-Fe2+ series from clinochlore to chamosite and biotite (as an analog of the 2:1 layer in chlorite) were investigated using thermogravimetry coupled to quadrupole mass spectrometry (TG-MS). A fast-ramp heating protocol was applied to identify if and how hydrogen gas was released from the crystal structure and whether it was quantitatively related to structural Fe2+ content. Dehydroxylation and oxidative dehydrogenation were tested under inert and oxidizing conditions.H2 liberation confirmed the H2 gas production by oxidative dehydrogenation, as shown by an evolution of the m/z = 2 signal for chamosites, Fe-rich clinochlores, and biotite heated under nitrogen gas atmosphere. Along with H2 evolution, H2O (m/z = 18) was released, suggesting that dehydroxylation is a trigger for dehydrogenation. The higher the Fe2+ content in the studied chlorites, the more intense the H2 evolution, thus the higher the H2/H2O ratios. The products of ramp-heating to 1000 °C resulted in varying amounts of newly formed Fe3+ (from 7 to 22%), however, biotite that converted into oxybiotite underwent almost complete oxidation, indicating a stronger tendency of 2:1 layer to dehydrogenation. The observed concurrent, but independent mechanisms of H2 and H2O evolution produced a feasible model of the thermal decomposition of chlorites.Despite O2 availability under oxidizing condition, the Fe2+ oxidation was not driven by attaching oxygen anions to the phyllosilicate structure, but also by dehydrogenation. Hydrogen was not detected using MS for any tested sample heated in synthetic air because any H2 if released was instantaneously combined with external O2, which resulted in an excess H2O MS signal not matched by mass loss on the TG profiles of chamosite and biotite. Without coupling of the evolved gas analysis with TG, the excess H2O produced by dehydrogenation in the O2-bearing carrier gas would result in misleading interpretations of dehydroxylation.Methodological and geological implications of the TG-MS experiments are discussed. The oxidation of Fe2+ in all Fe2+-containing phyllosilicates proceeds with simultaneous H2 gas release that is not dependent on oxygen fugacity nor temperature during the mineral formation. Therefore, the correlation between Fe3+/Fe2+ and remaining hydrogen in the structure must be considered during modeling the conditions that involve chlorite as geothermobarometer. H2 release during heating is proposed as an indicator of oxidative dehydrogenation of Fe2+-bearing minerals on Mars.

Cutaneous sensory nerve-mediated microvascular vasodilation in normotensive and prehypertensive non-Hispanic Blacks and Whites.

Relative to non‐Hispanic Whites, non‐Hispanic Blacks are disproportionately affected by elevated blood pressure (BP). It is unknown whether race or subclinical increases in BP affect the ability of cutaneous sensory nerves to induce cutaneous microvascular vasodilation. Sixteen participants who self‐identified as non‐Hispanic Black (n = 8) or non‐Hispanic White (n = 8) were subgrouped as normotensive or prehypertensive. Participants were instrumented with three intradermal microdialysis fibers: (a) control, (b) 1 μM sodium nitroprusside (SNP), an exogenous nitric oxide (NO) donor, and (c) 20 mM NG‐nitro‐l‐arginine methyl ester (L‐NAME), a non‐selective NO synthase inhibitor. A slow local heating protocol (33–40°C, 0.1°C/min) was used to assess the onset of cutaneous sensory nerve‐mediated vasodilation (temperature threshold) and skin blood flow was measured using laser‐Doppler flowmetry. At control sites, the temperature threshold occurred at a higher temperature in non‐Hispanic Blacks (normotensive: 37.2 ± 0.6°C, prehypertensive: 38.9 ± 0.5°C) compared to non‐Hispanic Whites (normotensive: 35.2 ± 0.8°C, prehypertensive: 35.2 ± 0.9°C). L‐NAME shifted the temperature threshold higher in non‐Hispanic Whites (normotensive: 37.8 ± 0.7°C, prehypertensive: 38.2 ± 0.8°C), but there was no observed effect in non‐Hispanic Blacks. SNP did not affect temperature threshold in non‐Hispanic Whites, but shifted the temperature threshold lower in non‐Hispanic Blacks (normotensive: 34.6 ± 1.2°C, prehypertensive: 34.8 ± 1.1°C). SNP mitigated differences in temperature threshold across all groups. There was no effect found for BP status in either the non‐Hispanic Black or non‐Hispanic White groups. These data suggest that reduced NO bioavailability affects the ability of cutaneous sensory nerves to induce microvascular vasodilation in young, otherwise healthy non‐Hispanic Blacks.

Induction heating by magnetic microbeads for pasteurization of liquid whole eggs

It is a challenge to pasteurize higher-viscosity and heat-sensitive foodstuffs via traditional convective heat transfer. Herein, we demonstrate the potential application of magnetic induction heating (MIH) as a novel uniform heating method applied in the pasteurization of liquid whole eggs (LWEs). Upon exposure to an alternating magnetic field (AMF), the magnetic microbeads with a large size (50 μm) generated heat via the magnetic hysteresis effect, providing accurate and homogeneous heating due to the high specific absorption rate (SAR) of 3108.4 ± 30.6 W/(g Fe) and a homogeneous particle dispersion in high-viscosity food media. A 7.6 log reduction of Salmonella Enteritidis could be achieved in LWEs treated by MIH at 68 °C and 60 s, which was comparable to the inactivation performance of the convective heating protocol at 60 °C and 210 s (6.0 log reduction). Importantly, MIH showed a critical temperature-time regime to prevent the coagulation of egg proteins, thus maintaining the quality attributes associated with fresh LWEs. The obtained results suggested that MIH could be a potential alternative to conventional convective heating for pasteurization applications.