Ambient Laboratory Research Articles

Remodeling of skeletal muscle myosin metabolic states in hibernating mammals.

Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators, Ictidomys tridecemlineatus and Eliomys quercinus and larger hibernators, Ursus arctos and Ursus americanus. We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in U. arctos and U. americanus during hibernation, whilst in I. tridecemlineatus and E. quercinus, changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20 °C). Upon repeating loaded Mant-ATP chase experiments at 8 °C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77-107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in I. tridecemilineatus, which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis.

Remodeling of skeletal muscle myosin metabolic states in hibernating mammals

Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators, Ictidomys tridecemlineatus and Eliomys quercinus and larger hibernators, Ursus arctos and Ursus americanus. We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in U. arctos and U. americanus during hibernation, whilst in I. tridecemlineatus and E. quercinus, changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20 °C). Upon repeating loaded Mant-ATP chase experiments at 8 °C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77–107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in I. tridecemilineatus, which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis.

METACASPASE8 (MC8) Is a Crucial Protein in the LSD1-Dependent Cell Death Pathway in Response to Ultraviolet Stress.

LESION-SIMULATING DISEASE1 (LSD1) is one of the well-known cell death regulatory proteins in Arabidopsis thaliana. The lsd1 mutant exhibits runaway cell death (RCD) in response to various biotic and abiotic stresses. The phenotype of the lsd1 mutant strongly depends on two other proteins, ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) and PHYTOALEXIN-DEFICIENT 4 (PAD4) as well as on the synthesis/metabolism/signaling of salicylic acid (SA) and reactive oxygen species (ROS). However, the most interesting aspect of the lsd1 mutant is its conditional-dependent RCD phenotype, and thus, the defined role and function of LSD1 in the suppression of EDS1 and PAD4 in controlled laboratory conditions is different in comparison to a multivariable field environment. Analysis of the lsd1 mutant transcriptome in ambient laboratory and field conditions indicated that there were some candidate genes and proteins that might be involved in the regulation of the lsd1 conditional-dependent RCD phenotype. One of them is METACASPASE 8 (AT1G16420). This type II metacaspase was described as a cell death-positive regulator induced by UV-C irradiation and ROS accumulation. In the double mc8/lsd1 mutant, we discovered reversion of the lsd1 RCD phenotype in response to UV radiation applied in controlled laboratory conditions. This cell death deregulation observed in the lsd1 mutant was reverted like in double mutants of lsd1/eds1 and lsd1/pad4. To summarize, in this work, we demonstrated that MC8 is positively involved in EDS1 and PAD4 conditional-dependent regulation of cell death when LSD1 function is suppressed in Arabidopsis thaliana. Thus, we identified a new protein compound of the conditional LSD1-EDS1-PAD4 regulatory hub. We proposed a working model of MC8 involvement in the regulation of cell death and we postulated that MC8 is a crucial protein in this regulatory pathway.

A Prognostic Approach to the Resonance Failure Problem by Triple Sensing Technology

Within this study, resonance phenomenon, which is one of the crucial problems in mechanical constructions, has been analyzed with respect to oil starvation failure in a ball bearing. A unique test rig is designed, constructed, and placed in a laboratory ambience. A ball bearing on the electrical motor, which is a component of the test rig, has been selected for acquisition of data within triple sensing technology in vibration, acoustic, and electrical consumption through testing conditions. The target of that study is condition monitoring of oil starvation fault and resonance fault for comparison of various predictive maintenance methods. The testing was carried out within the electrical frequency of 40.5 Hz, which actuated the electrical motor in order to identify the rotation speed. According to the analyzed results, oil starvation fault and resonance fault is most accurately inspected by vibration analysis.

Triaxial Cell for Determining Shielded Cable Transfer Impedance During Environmental Stress

Transfer impedance is a main characteristic to describe the shielding performance of shielded cables at least up to 1 GHz. Traditionally, methods, such as line-injection and triaxial cell, have been used to characterize it at ambient laboratory conditions. While the ambient laboratory conditions might represent appropriate environmental conditions for some industries, in others, such as automotive, they are only a small subset of the real conditions. Thus, there is a need to characterize the transfer impedance over different environmental conditions. In this article, the authors present and verify a new triaxial cell design that is aimed to provide reliable measurements during high thermal and mechanical stresses. First, the cell performance is compared with a commercial cell at laboratory ambient conditions. Then, measurements are performed with the new cell at highly accelerated life testing conditions. Under these high thermal and mechanical stress conditions, the cell performance is verified, and results on typical shielded cable performance under the same conditions are given.

Linking Patient Experience to Customer Delight in the Private Laboratory Service

The goal of this study was to analyse the influence of the antecedents of patient experience, namely staff appearance, laboratory staff attitude, information clarity, staff responsiveness, laboratory ambience, phlebotomy process, laboratory technology, and report results, which furtherly generate customer delight and drive favourable intentions such as revisit intentions to the laboratory and willingness to share and post on social media. By extending earlier studies and using data from a leading private clinical laboratory service, this study suggests a new insight. A quantitative study with a survey is used with a cross-sectional data approach. The sample was taken purposively from customers who have had laboratory services at the laboratory, particularly from customers who have undergone the phlebotomy process. The 186 samples that complied with the criteria were examined using the PLS-SEM method. The findings demonstrated that the eight antecedents show a high probability of influencing the patient experience, with the phlebotomy process found as the predominant antecedent, followed by laboratory staff attitude and patient perception of laboratory technology. Further, this study found strong evidence that patient experience could generate customer delight, which drives the revisit intention and willingness to share and post positive things on social media. Openness is found to strengthen that process. The results of this study revealed that the higher the patient’s experience through their journey, the higher the probability of delight could exist in the context of service provided in the private clinical laboratory. Thus, it is worth considering by the clinic management to develop a more effective business.

Indomethacin: Effect of Diffusionless Crystal Growth on Thermal Stability during Long-Term Storage.

Differential scanning calorimetry and Raman spectroscopy were used to study the nonisothermal and isothermal crystallization behavior of amorphous indomethacin powders (with particle sizes ranging from 50 to 1000 µm) and their dependence on long-term storage conditions, either 0-100 days stored freely at laboratory ambient temperatures and humidity or placed in a desiccator at 10 °C. Whereas the γ-form polymorph always dominated, the accelerated formation of the α-form was observed in situations of heightened mobility (higher temperature and heating rate), increased amounts of mechanically induced defects, and prolonged free-surface nucleation. A complex crystallization behavior with two separated crystal growth modes (originating from either the mechanical defects or the free surface) was identified both isothermally and nonisothermally. The diffusionless glass-crystal (GC) crystal growth was found to proceed during the long-term storage at 10 °C and zero humidity, at the rate of ~100 µm of the γ-form surface crystalline layer being formed in 100 days. Storage at the laboratory temperature (still below the glass transition temperature) and humidity led only to a negligible/nondetectable GC growth for the fine indomethacin powders (particle size below ~150 µm), indicating a marked suppression of GC growth by the high density of mechanical defects under these conditions. The freely stored bulk material with no mechanical damage and a smooth surface exhibited zero traces of GC growth (as confirmed by microscopy) after >150 days of storage. The accuracy of the kinetic predictions of the indomethacin crystallization behavior was rather poor due to the combined influences of the mechanical defects, competing nucleation, and crystal growth processes of the two polymorphic phases as well as the GC growth complex dependence on the storage conditions within the vicinity of the glass transition temperature. Performing paired isothermal and nonisothermal kinetic measurements is thus highly recommended in macroscopic crystallization studies of drugs with similarly complicated crystal growth behaviors.

Proteome analysis of Campylobacter jejuni poultry strain 2704 survival during 45 min exposure to peracetic acid

Peracetic acid (PAA) applied to whole poultry carcasses can reduce the number of Campylobacter, a leading cause of human gastroenteritis. However, previous modelling experiments indicated that Campylobacter survived in greater numbers when pre-treated with a thermal stress equivalent to poultry processing scalding prior to chilling with PAA than when subject to chilling with PAA only. To better understand how Campylobacter responds to PAA, proteomes of C. jejuni poultry strain 2704 were measured after exposure to PAA (60 ppm, pH 4.0) for 45 min under laboratory ambient conditions (approximately 23 °C) to establish a foundational map of survival mechanism before combining with other stresses. Analysis of 580 quantified proteins did not indicate a triggered “peroxide shock” response, nor were common heat shock responses detected. Thioredoxin, iron homeostatic, peroxiredoxins and cytochrome c peroxidases became more abundant suggesting that PAA disturbed cytoplasmic redox homeostasis resulting in antioxidant activation and increased prioritisation of iron homeostasis. The PAA treatment led to responses that included an increased priority for oxidative phosphorylation and a simultaneous decrease in central metabolism associated protein abundances. Lon protease was induced suggesting it has a role in maintaining homeostasis during non-thermal stress. Proteins in flagella and chemotaxis became more abundant though whether PAA has a chemorepellent effect requires further investigation. Overall, the proteome data suggests there was a rapid cellular response to applied PAA stress in the first 15 min with the adaptation to the stress completing between 30 and 45 min. The findings will help guide PAA implementation in commercial poultry processing in terms of processing location and length of application.

Effect of Seed Coat Characteristics on Seed Quality in Soybean [Glycine max (L) Merrill] Genotypes with Contrasting Seed Longevity Traits

Background: The soybean seed is highly susceptible to field weathering and mechanical damages which adversely affect its longevity. Non-availability of good quality seed and post-harvest maintenance of prescribed level of seed germination and vigour until immediate planting season is the major constraint for soybean seed production. In soybean, the seed coat is one of the main determinants of seed germination, vigour and longevity potentials. Methods: In view of the same, the present study was conducted during 2015-16 and 2016-17 on 24 soybean genotypes having contrasting seed longevity traits. Freshly harvested seeds were stored for eight months under laboratory ambient environment (25±2°C and 65±5% RH) for evaluation of seed coat properties which are helpful in protecting the seeds from mechanical damage during pre- and post-harvest operations and study its relation with the seed quality. Result: Black, small-seeded soybean genotypes with white hilum were found to be better storers. Thick seed coat and higher seed coat (%) with more and uniform hours glass cells attributed to better seed quality for these genotypes. Parameters like seed coat (%), lignin content and mechanical strength remained unchanged during eight months laboratory ambient storage. Based on these observations, genotypes AMSS-34 and G-2265 were identified as better genotypes, which may be exploited in soybean crop improvement programme.

Ring Contraction of a Tungstacyclopentane Supported on Silica: Direct Conversion of Ethylene to Propylene.

The reaction of W(NAr)(13C4H8)(OSiPh3)2 (1) (NAr = 2,6-diisopropylphenylimido) with silica partially dehydroxylated at 700 °C (SiO2-700) is highly dependent on the reaction conditions. The primary product of this reaction is W(NAr)(13C4H8)(OSiPh3)(OSi(O-)3) (2) when the reaction is carried out in the dark. Grafting 1 onto SiO2-700 in ambient lab light results in the formation of 2, W(NAr)(13CH213CH2)(OSiPh3)(OSi(O-)3) (4), and one isomer of square-pyramidal W(NAr)(13CH213CH(13Me)13CH2)(OSiPh3)(OSi(O-)3) (3). Heating 2 to 85 °C for 6 h results in the formation of 3, 4, W(NAr)(13CH(13Me)13CH213CH2)(OSiPh3)(OSi(O-)3) (5), and W(NAr)((13CH2)213CH(13Me)(13CH2)2)(OSiPh3)(OSi(O-)3) (6). Photolysis of 2 with blue LEDs (λmax = 450 nm) produces 4, both isomers of 3, 5, and free ethylene. In the presence of excess ethylene and blue LED irradiation at 85 °C, 1/SiO2-700 catalyzes the direct conversion of ethylene to propylene.

An improvement in un-Encapsulated perovskite solar cell’s environmental stability via introduction of an electrode interface layer

ABSTRACT Perovskite solar cells (PSCs) have shown power conversion efficiency (PCE) up to 25.5%,but they are still struggling with their poor environmental stability. We have improvedthe ecological stability of un-encapsulated PSCs via interface modification of the topmetal electrode. We used CH3NH3PbI3-xClx perovskite as the light absorber and Ag metal as the top electrode. The interfaceof Ag electrode was modified by introducing a thin layer of MoOx/Al before Ag. We observed that MoOx/Al interlayer before Ag imparts better stability to the devices than conventional Ag electrode only. We found that MoOx/Al interlayer impedes the diffusion of oxygen and metalelectrode intothe perovskite film and considerably halts the device degradation upon beingkept for about 350 h under laboratory ambient conditions (room temperature 25±2oC and humidity 40±5%). This work mainly highlights the role of interfaces in PSCs degradation, and will help to addressthe stability issues in PSCs.

Music Attenuates The Perception Of Dyspnea During Exercise With Headphones In Healthy Individuals

Dyspnea limits physical exertion and may cause early cessation of exercise or discouragement from participating in exercise altogether. To distract from dyspnea, many individuals listen to music while exercising which can alter afferent feedback from breathing sounds; however, it is currently unknown whether auditory distraction with music mitigates exertional dyspnea in healthy individuals. PURPOSE: The purpose was twofold: 1) to determine whether listening to music through headphones affects the sensory (breathing intensity; BI) and/or affective (breathing unpleasantness; BU) components of dyspnea during exercise at different intensities, and 2) to assess whether music impacts exercise performance by influencing an individual’s self-selected workload. METHODS: Twenty-two recreationally active individuals (24 ± 3 yr, 10 women) performed two 5-min constant loads (10% below/above gas exchange threshold-GET) and an 8 km (4.97mi) cycling time trial with either ambient lab noise or self-selected music (via headphones), in a randomized crossover design. BI, BU, and ventilation (VE) were measured at each minute of the constant loads and every 2 km of the time trial. Ratios of BU/VE and BI/VE were used to examine the gain in dyspnea during the self-paced time trial. Data are presented as mean ± SD. RESULTS: In the first and final minute of the 10% below GET trial, BU was less with music (14.0 ± 11.4 mm vs. 19.8 ± 12.5 mm, P = 0.03 and 29.3 ± 16.7 mm vs. 34.8 ± 15.4 mm, P = 0.04, respectively). In every minute of the 10% above GET trial, BU was less with music (P < 0.05) despite no difference in VE between conditions. During the time trial, VE was not different between conditions; however, with music, BU/VE was significantly attenuated by 13-17% (P < 0.05). Heart rate and self-selected power output were greater during the time trial with music (P < 0.05). CONCLUSIONS: The application of music through headphones appears to modify ventilatory afferent feedback, significantly mitigating the sensation of dyspnea during exercise. Additionally, and most notably, music changed the accretion of dyspnea per unit of VE leading to a higher self-selected workload. The dyspnea-reducing intervention of self-selected music may improve exercise tolerance, performance, and promote adherence to regular aerobic exercise.

Experimental Thermal Response Study of Multilayered, Encapsulated, PCM-Integrated Building Construction Materials

Thermal energy storage integration using phase change materials (PCMs) in buildings has great potential for energy conservation and greenhouse gas (GHG) emission reduction. Cutting-edge research and innovative ideas are required when using multilayered PCMs within typical construction materials to take advantage of their heat storage capability over a wide temperature range within buildings. This current study was carried out to experimentally test the efficacy of using dual PCMs RT28HC and RT21HC with different melting temperature ranges (28 °C and 21 °C) under variable thermal loading. The transient thermal response of various PCM-based configurations of concrete and cement blocks at different temperature inputs was obtained to determine the effectiveness of dual PCMs and their optimized configuration under experimental laboratory conditions. The range of the temperature input was varied from 22 °C to 50 °C, suitable for hot climatic conditions such as those in Pakistan. Laboratory ambient temperatures remained at ~17 °C for all experimental tests. Moreover, the results were compared using two parameters, i.e., decrement factor (DF) and time lag (TL). With DF and TL values of 0.10 and 5.72, respectively, in the high-temperature heating (HTH) regime and a low DF value of 0.08 and high TL of 5.17 in the moderate-temperature heating (MTH) regime, the RT28HC–RT21HC combination proved to be the most effective. The application of the RT28HC–RT21HC combination provided up to a 54.3% reduction in indoor temperatures in the HTH regime. This research contributes through experimental validation that these novel configurations are capable of providing substantial improvement in indoor thermal comfort.

Dyspnea Is Attenuated by Auditory Distraction via Music with Headphones during Exercise in Healthy Individuals.

This study aimed to determine whether listening to music through headphones (a) affects the sensory (breathing intensity [BI]) and/or affective (breathing unpleasantness [BU]) components of dyspnea during exercise at different intensities and (b) affects exercise performance. Twenty-two recreationally active individuals (24 ± 3 yr, 10 women) performed two 5-min constant loads (10% below/above gas exchange threshold [GET]) and an 8-km cycling time trial with ambient laboratory noise or self-selected music in a randomized crossover design. BI, BU, and ventilation ( V̇E ) were measured at each minute of the constant loads and every 2 km of the time trial. Ratios of BU/ V̇E and BI/ V̇E were used to examine the gain in dyspnea during the time trial. In the 10% below GET trial, BU was reduced in the first ( P = 0.03) and final ( P = 0.04) minutes. In the 10% above GET trial, BU and BI were reduced with music ( P < 0.05). During the time trial with music, BU/ V̇E was significantly attenuated by 9%-13% ( P < 0.05) despite a greater heart rate and self-selected power output ( P < 0.05). Music through headphones mitigated the sensation of dyspnea and changed the accretion of dyspnea per unit increase in V̇E leading to a higher self-selected workload during self-paced exercise. The dyspnea-reducing intervention of self-selected music may improve exercise tolerance and performance and promote adherence to regular aerobic exercise.

Smartphone-based automated estimation of plasma creatinine from finger-pricked blood on a paper strip via single-user step sample-to-result integration

Measuring creatininelevels in blood plasma is one of the most commonly used means of routine monitoring of renal function. Point-of-care devicesfor creatinine level estimation potentially allow rapid measurement, facilitating continuous monitoring of vulnerable patients. However, a majority of such devices currently available is constrained by several factors such as lack of simplicity in fabrication and operation (including plasma separation), a limited regime of efficacy, compromised reagent stability, and elevated costs. Here, we report the invention of a simple-to-fabricate and easy-to-use paper strip for rapid evaluation of plasma creatinine levels (ranging from 0.1 to 15 mg dL-1) in an integrated single-step process. For the testing, one drop of whole blood is first dripped onto the calcium salt-functionalized sample pad of the strip. Subsequently, blood plasma separation occurs due to spontaneous aggregation of red blood cells (RBCs) in the presence of calcium ions. The plasma spontaneously traverses into the reaction zone of the test-strip via capillary action where it reacts with previously dispensed alkaline picrate reagent, resulting in a colorimetric signal. Smartphone-interfaced imaging and image analytics of the reaction spot renders the dissemination of the test result in a turn-around time of about 2–3 min, without necessitating additional device interfacing. High efficacy of performance is established by validating with the results obtained from laboratory-benchmarked biochemical auto-analyzer, exhibiting an accuracy of 94%, and the coefficient of variation ranging from 0.64 to 6.4%. Suitability of use in extreme resource-limited settings is established by favorable stability of the reagents outside controlled laboratory ambience and engagement of unskilled personnel to execute the testing procedure with uncompromised accuracy.

Atomic Insights of Stable, Monodispersed CsPbI3−xBrx (x = 0, 1, 2, 3) Nanocrystals Synthesized by Modified Ligand Cell

AbstractSynthesis of monodispersed, stable halide, and mixed halide perovskite nanocrystals by hot‐injection approach is still challenging due to the fast reaction kinetics and unrevealed ligand chemistry. The atomic scale imaging of perovskite nanocrystals using transmission electron microscopy (TEM) is also challenging because of their structural degradation due to high electron dose and soft nature of perovskites. Here, a novel technique is proposed to synthesize pure cubic phase, monodispersed, stable CsPbX3 (X = I/Br) nanocrystals by simply modifying ligand chemistry using olive oil, which also leads to realization of tuneable composition mixed halide perovskites by simple physical mixing. Here, the atomic scale images and the probable distribution of Cs, Pb, and I/Br atoms in single halide and mixed halide perovskites via high‐resolution TEM microscopy are presented. The estimated atomic distance (PbPb and PbI/Br) is strongly corroborated with the VESTA structure. Interestingly, the lattice constant (d‐value) of the synthesized nanocrystals is smaller (≈3%) than the theoretical predicted one, leading to a higher phase stability in laboratory ambient conditions (45–55% humidity, 300 K). The theoretical analysis using density functional theory enlightens the understanding of higher stability of CsPbI2Br along with the maximum optical absorption in the visible regime, as a preferable material for the photovoltaic applications.

Breakdown and Healing of Tungsten-Oxide Films on Microelectromechanical Relay Contacts

This work discusses the electrical break down of tungsten oxide films that form on contacting surfaces of tungsten electrodes in micro-electro-mechanical (MEM) relays. Electrical tests were applied to the contacts of 27 devices to measure the voltage, current and charge required to break down the oxide films, and also to measure the change in current through the contacts as the film healed. The oxide breaks down when an average of 58 <inline-formula> <tex-math notation="LaTeX">$\mu \text{C}$ </tex-math></inline-formula> of electronic charge passes through the oxide, which usually requires applying 1&#x2013;2 V to drive 100 nA-<inline-formula> <tex-math notation="LaTeX">$10~\mu \text{A}$ </tex-math></inline-formula> of current through the contact. The tungsten oxide heals quickly in laboratory ambient conditions: applying 0.5 V to a contact immediately after breaking down an oxide results in a contact current greater than <inline-formula> <tex-math notation="LaTeX">$5~\mu \text{A}$ </tex-math></inline-formula>, but the same test only induces 1 nA of current 1&#x2013;5 minutes later. The reduction in contact current with time follows a power law, which is characteristic of charge relaxation in oxides. Additionally, Holm&#x2019;s experiment shows that current conduction through the contacts is dominated by tunneling through an oxide. These facts together suggest that the break down and healing are electrical processes related to trap accumulation and relaxation in the tungsten oxide. [2021-0161]

Ultrashort pulsed laser ablation of granite for stone conservation

This paper investigates the ultrashort pulsed laser ablation of a high heritage value Australian granite comprising quartz, feldspar (plagioclase and minor potassium-feldspar), and Mg-Fe-bearing minerals (biotite and hornblende). This work is relevant to laser cleaning and texturing of heritage stone surfaces and the preparation and maintenance of granite in other applications. The experiments were undertaken in an ambient lab air environment (23 ± 2 °C and 20–40 % relative humidity) with nitrogen blow, on dry surfaces using 275 fs duration laser pulses at 1029 nm. The ablation behaviour of the different granite minerals was experimentally studied in a fluence range of 1– 17 J·cm−2 in the single shot per spot regime and the ablated surfaces were assessed with a multi-analytical approach including optical and scanning electron microscopy, Raman spectroscopy and optical profilometry. The ablation threshold was established for each different mineral in the stone. Biotite is the most readily ablated, with an ablation threshold of 1.1 ± 0.1 J·cm−2. It is followed by hornblende at 1.3 ± 0.1 J·cm−2, plagioclase at 1.4 ± 0.1 J·cm−2 and quartz, at 1.6 ± 0.1 J·cm−2, which is the most resistant component mineral. Following the electrostatic laser ablation model, the ablation thresholds were theoretically estimated for each mineral phase and demonstrated to be in reasonable agreement with the experimental results. The highest ablation efficiency of the granite as a whole was determined to occur at a fluence of 8.4 J·cm−2, giving an ablation efficiency of 0.27 ± 0.03 mm3·(min·W)−1 in terms of volume removal. From the experimental data, a maximum laser fluence for conservation cleaning was determined at 1.0 ± 0.1 J·cm−2, at which no discernible change or detrimental effect on the granite was observable. Above this fluence, morphological changes were induced in the stone and higher fluences should therefore be avoided for conservation cleaning.

Urbach Energy and Open-Circuit Voltage Deficit for Mixed Anion-Cation Perovskite Solar Cells.

The Urbach energy indicating the width of the exponentially decaying sub-bandgap absorption tail is commonly used as the indicator of electronic quality of thin-film materials used as absorbers in solar cells. Urbach energies of hybrid inorganic-organic metal halide perovskites with various anion-cation compositions are measured by photothermal deflection spectroscopy. The variation in anion-cation composition has a substantial effect on the measured Urbach energy and hence the electronic quality of the perovskite. Depending upon the compositions, the Urbach energy varies from 18 to 65 meV for perovskite films with similar bandgap energies. For most of the perovskite compositions studied here including methylammonium (MA) + formamidinium (FA)-based Pb iodides, mixed Sn + Pb narrow-bandgap perovskites with low or intermediate Sn contents, and wide-bandgap FA + Cs- and I + Br-based perovskites, the correlation between the Urbach energy of the perovskite thin film and open-circuit voltage (VOC) deficit for corresponding solar cells shows a direct relationship with reduction of the Urbach energy occurring with a beneficial decrease in the VOC deficit. However, due to issues related to material quality, impurity phases and stability in laboratory ambient air, and unoptimized film processing techniques, the solar cells incorporating Cs-based inorganic and mixed Sn + Pb perovskites with a higher than optimum Sn content show a higher VOC deficit even though the corresponding films show a lower Urbach energy.

Temperature Dependence of Nuclear Magnetic Resonance Relaxation Time in Carbonate Reservoirs

Summary Nuclear magnetic resonance (NMR)-based interpretation models are commonly calibrated using laboratory ambient core NMR measurements. For applying the core calibrated models to downhole NMR logging interpretation, the difference between the NMR responses measured at ambient and reservoir temperature needs to be evaluated. The temperature dependence of NMR relaxation time in high-quality (HQ) carbonate reservoirs has been studied, and NMR temperature dependence models were established using data analytic methods. In this paper, we extend our early studies on temperature dependence of NMR relaxation time to low-quality (LQ) carbonate formations. For more than 95% of the LQ samples investigated, NMR relaxation time shows a positive correlation with temperature. The correlation is similar to that observed in HQ carbonate rocks but slightly less significant. Temperature-dependent correlations for predicting the geometric mean of NMR transverse relaxation time (T2,GM) from a measured temperature to any other temperature were derived from HQ to LQ carbonate rocks independently first, then a unified T2,GM correlation was derived including both the HQ and LQ carbonate reservoirs. Predicting NMR transverse relaxation time T2 distribution from one temperature to other temperatures was achieved using a dimension reduction approach involving the principal component analysis (PCA) technique. It was found that the T2 distributions at any given temperature for both HQ and LQ carbonate reservoirs can be predicted robustly from the T2 distributions at the ambient temperature by representing the T2 distributions with principal components (PCs) at the ambient temperature and then using these PCs to predict the PCs at a different temperature. The optimal number of PC components depends on the multimodality of the T2 distribution. This work extends the validity range of the data analytic methods, in particular parameter and dimension reduction methods, that quantify the temperature dependence of carbonate NMR properties. The new NMR temperature model enables the integration of NMR laboratory studies and downhole measurements for advanced petrophysical analyses in a wide range of carbonate reservoirs.