Long-term warming increased carbon sequestration capacity in a humid subtropical forest.

Tropical and subtropical forests play a crucial role in global carbon (C) pools, and their responses to warming can significantly impact C-climate feedback and predictions of future global warming. Despite earth system models projecting reductions in land C storage with warming, the magnitude of this response varies greatly between models, particularly in tropical and subtropical regions. Here, we conducted a field ecosystem-level warming experiment in a subtropical forest in southern China, by translocating mesocosms (ecosystem composed of soils and plants) across 600 m elevation gradients with temperature gradients of 2.1°C (moderate warming), to explore the response of ecosystem C dynamics of the subtropical forest to continuous 6-year warming. Compared with the control, the ecosystem C stock decreased by 3.8% under the first year of 2.1°C warming; but increased by 13.4% by the sixth year of 2.1°C warming. The increased ecosystem C stock by the sixth year of warming was mainly attributed to a combination of sustained increased plant C stock due to the maintenance of a high plant growth rate and unchanged soil C stock. The unchanged soil C stock was driven by compensating and offsetting thermal adaptation of soil microorganisms (unresponsive soil respiration and enzyme activity, and more stable microbial community), increased plant C input, and inhibitory C loss (decreased C leaching and inhibited temperature sensitivity of soil respiration) from soil drying. These results suggest that the humid subtropical forest C pool would not necessarily diminish consistently under future long-term warming. We highlight that differential and asynchronous responses of plant and soil C processes over relatively long-term periods should be considered when predicting the effects of climate warming on ecosystem C dynamics of subtropical forests.

Fabrication and stability of W/O/W emulsions stabilized by gum arabic and polyglycerol polyricinoleate.

BACKGROUND: In order to study the effect of adsorption of surfactant at the two interfacial layers on emulsion stability, the kinetically stable water-in-oil-in-water (W/O/W) emulsion carriers were prepared using polyglycerol polyricinoleate (PGPR) and gum arabic (GA) as emulsifiers. The relationship between the adsorption of the surfactant and the stability mechanism of the emulsions was elucidated. RESULTS: When the contents of PGPR and GA were low, the interfaces between oil and the inner and outer water phases, respectively, could not be completely covered. However, when the concentration of PGPR was higher than 60 g kg-1 , the excess PGPR was adsorbed on the interface between the oil phase and the outer water phase. When the concentration of GA reached 80 g kg-1 , more GA was adsorbed to the oil-in-water interface. Moreover, the presence of PGPR on the interface could reduce the adsorption capacity of GA. Two types of kinetically stable emulsions were obtained by optimizing the interface composition (60 g kg-1 GA/80 g kg-1 PGPR and 60 g kg-1 PGPR/80 g kg-1 GA). The kinetically stable W/O/W emulsions prepared in this study were successfully used to encapsulate a hydrophilic vitamin (vitamin B12) with an encapsulation efficiency (EE) of 80% and release efficiency (RE) of 95%. The interfacial adsorption GA can accelerate the hydrolysis of fat. CONCLUSION: Overall, this study provides a new strategy for the preparation of W/O/W emulsions, which might be beneficial for application in food, cosmetic, chemical, and pharmaceutical industries. © 2023 Society of Chemical Industry.

Electronic Structure and Aromaticity of an Unusual Cyclo[18]carbon Precursor, C18 Br6.

Herein, the electronic structure and bonding character of the stable cyclo[18]carbon (C18 ) precursor, C18 Br6 , are thoroughly characterized by molecular orbital (MO), density of states (DOS), bond order (BO), and interaction region indicator (IRI) analyses. The delocalization characters of out-of-plane and in-plane π-electrons (labeled as πout - and πin -electrons, respectively) in bonding regions were examined using localized orbital locator (LOL) and electron localization function (ELF). The aromaticity was investigated, studying the molecular magnetic response to external magnetic field by computing the magnetically induced current density (Jind ), iso-chemical shielding surface (ICSS), anisotropy of the induced current density (AICD), and the induced magnetic field (Bind ). All these analyses indicate that C18 Br6 is a globally aromatic species with lower aromaticity than C18 , and the blocking of in-plane π-conjugation (labeled as πin -conjugation) by the presence of -Br substituents in it is the underlying cause for the weakening of molecular aromaticity.

Aggregation and Growth Mechanism of Ovalbumin and Sodium Carboxymethylcellulose Colloidal Particles under Thermal Induction.

Ovalbumin (OVA)/sodium carboxymethylcellulose (CMC) colloidal particles were prepared with different compactness and morphologies by regulating the interaction between proteins and polysaccharides during heating. Electrostatic interactions between the amine groups of OVA (-NH3+) and carboxyl groups of CMC (-COO-) enhanced complex formation. The protein conformation change benefited the hydrophobic interaction between the particles. Proteins in colloidal particles were unfolded/folded under thermal induction to form aggregates having more ß-sheet structures. When the OVA/CMC ratio was 1:2, the initially loosely connected OVA/CMC aggregation changed into a uniform sphere between 25 and 90 °C. The mass ratio of OVA to CMC within the final colloidal particle (90 °C) was about 1:1.4. The OVA/CMC particle stability was maintained with hydrogen bonding, hydrophobicity, and disulfide bond. When OVA levels were predominant, OVA and CMC developed an approximately hollow sphere. Moreover, the final colloidal particle composition showed the OVA-to-CMC ratio as 3:1 (w/w). OVA bound into colloidal particle pores to increase compactness. Moreover, OVA and CMC bound to the colloidal particle while the particle shrank, thereby increasing the compactness of colloidal particles. There was a significant decrease in ABTS•+ scavenging activity of curcumin compared with that of the particles with a ratio of 1:2. Thus, the rational adjustment of the structure of colloidal particles could effectively enhance their functional characteristics, providing a new way for the controlled release of the active ingredients.

Size dependence of optical nonlinearity for H-capped carbon chains, H-(CC)n-H (n = 3-15): analysis of its nature and prediction for long chains.

Based on a computational approach that can accurately describe their geometric structures and electronic spectra, we have theoretically studied the nonlinear optical (NLO) properties of H-capped carbon chains, H-(CC)n-H (n = 3-15), for the first time. Special attention was paid to the size dependence of the molecular (hyper)polarizability of these species through the nonlinear fitting of the data, which formed two power-law formulas of αiso(∞) = -0.206 + 0.264n1.498 and γ‖(∞) = -0.624 + 0.006n3.368 and was thoroughly discussed at the electronic structure level by in-depth wavefunction analyses. The fundamental gap (ΔE) between vertical ionization energy (VIE) and vertical electron affinity (VEA) is found to be related to the molecular (hyper)polarizability. The calculated (hyper)polarizability of the carbon chains H-(CC)n-H (n = 3-15) is more sensitive to the density functional theory (DFT) applied than to the basis set selected. The results are expected to provide theoretical guidance for the property prediction of arbitrarily long carbon chains not yet synthesized.

Low-loss adiabatic fiber-optic coupler for cryogenic photonics.

Recent developments in quantum light-matter coupled systems and quantum transducers have highlighted the need for cryogenic optical measurements. In this study, we present a packaged fiber-optic coupler with a coupling efficiency of over 50% for telecom wavelength light down to the mK temperature range. Besides the high coupling efficiency, our method enables sensitive photonic device measurements that are immune to mechanical vibrations present in cryogenic setups.

The impact of glycerol monostearate's similarity to fats and fatty acid composition of fats on fat crystallization, destabilization, and texture properties of ice cream.

BACKGROUND: Fat significantly affects the properties of ice cream. Prior studies have investigated the correlation between fat crystallization, fat destabilization, and ice cream quality. However, the role of fatty acid composition, the similarity between fat and emulsifier in these characteristics, and their impact on final product quality remains unclear. RESULTS: To investigate the influence of the fatty acid composition of fats, as well as their similarity to glycerol monostearate (GMS), on fat crystallization and destabilization during the aging and freezing stages, ice creams were formulated using a combination of two types of fats (coconut oil and palm olein) in five different ratios. In oil phases, decreased saturation of fatty acids (from 93.38% to 46.69%) and increased similarity to GMS (from 11.96% to 46.01%) caused a reduction in the maximum solid fat content. Moreover, the rise in unsaturated long-chain fatty acids (from 34.61% to 99.57%) and similarity to GMS enhanced the formation of rare and coarse fat crystals, leading to a sparse crystalline network. This, in turn, reduced the crystallization rate and the stiffness of the fat in emulsions. Assuming consistent overrun across all ice creams, the enhanced interactions between fat globules in ice cream improved its hardness, melting properties, and shrinkage. CONCLUSION: The crystalline properties of fat in emulsions were influenced by oil phases, impacting fat destabilization and ultimately enhancing the quality of ice cream. The present study offers valuable insights for the optimization of fat and monoglyceride fatty acid ester selection, with the potential to improve ice cream quality. © 2023 Society of Chemical Industry.

Photophysical properties and optical nonlinearity of cyclo[18]carbon (C18) precursors, C18-(CO)n (n = 2, 4, and 6): focusing on the effect of the carbonyl groups.

The electronic spectra and (hyper)polarizability of C18-(CO)n (n = 2, 4, and 6) are studied using theoretical calculations to reveal the effect of introducing carbonyl (-CO) groups on the molecular optical properties. Successive introduction of -CO groups is observed to cause a red-shift in the absorption spectrum, but maximum absorption of all molecules is mainly due to the charge redistribution within the C18 moiety. The (hyper)polarizabilities of the cyclocarbon oxides present an ascending trend with the -CO groups in the molecule, and the higher-order response properties are more sensitive. With (hyper)polarizability density analysis and (hyper)polarizability contribution decomposition, the fundamental reasons for the difference of (hyper)polarizability of different molecules are systematically discussed from the perspective of physical and structural origins, respectively. Significant optical resonances under the frequency-dependent fields are found for the (hyper)polarizabilities of the cyclocarbon oxides, which is in contrast to the insignificant influence on their polarizability.

Warming leads to more closed nitrogen cycling in nitrogen-rich tropical forests.

Warming may have profound effects on nitrogen (N) cycling by changing plant N demand and underground N supply. However, large uncertainty exists regarding how warming affects the integrated N dynamic in tropical forests. We translocated model plant-soil ecosystems from a high-altitude site (600 m) to low-altitude sites at 300 and 30 m to simulate warming by 1.0°C and 2.1°C, respectively, in tropical China. The effects of experimental warming on N components in plant, soil, leaching, and gas were studied over 6 years. Our results showed that foliar δ15 N values and inorganic N (NH4 -N and NO3 -N) leaching were decreased under warming, with greater decreases under 2.1°C of warming than under 1.0°C of warming. The 2.1°C of warming enhanced plant growth, plant N uptake, N resorption, and fine root biomass, suggesting higher plant N demand. Soil total N concentrations, NO3 -N concentrations, microbial biomass N and arbuscular mycorrhizal fungal abundance were decreased under 2.1°C of warming, which probably restricted bioavailable N supply and arbuscular mycorrhizal contribution of N supply to plants. These changes in plants, soils and leaching indicated more closed N cycling under warming, the magnitude of which varied over time. The closed N cycling became pronounced during the first 3 years of warming where the sustained reductions in soil inorganic N could not meet plant N demand. Subsequently, the closed N cycling gradually mitigated, as observed by attenuated positive responses of plant growth and less negative responses of microbial biomass N to warming during the last 3 years. Overall, the more closed N cycling under warming could facilitate ecosystem N retention and affect production in these tropical forests, but these effects would be eventually mitigated with long-term warming probably due to the restricted plant growth and microbial acclimation.

Equivalent Loading of Directed Arenes in Pd(II)-Catalyzed Oxidative Cross-Coupling of Aryl C-H Bonds at Room Temperature.

The unsymmetrical biaryls (Ar1-Ar2) produced by the catalytic cross-couplings of aryl halides (Ar1-halo) with aryl metallics (Ar2-M) in the loading ratio of 1:1 are popular in chemical synthesis. In contrast, there has been less precedence on the same biaryls produced effectively from two normal aryl C-H bonds with equivalent loading. Here, we report that, in a palladium/oxidant/acid catalytic system at room temperature, one arene (Ar1-H, 1 equiv) can highly selectively couple with the other one (Ar2-H, 1 equiv) to afford the target Ar1-Ar2 just by controlling the directing groups and the substituted groups on their phenyl rings. The utility of this one-one cross-coupling is also demonstrated by synthesis of a few bioactive molecules.

Mechanical bound states in the continuum for macroscopic optomechanics.

Bound states in the continuum (BICs), an emerging type of long-lived resonances different from the cavity-based ones, have been explored in several classical systems, including photonic crystals and surface acoustic waves. Here, we reveal symmetry-protected mechanical BICs in the structure of slab-on-substrate optomechanical crystals. Using a group theory approach, we identified all the mechanical BICs at the Γ point in optomechanical crystals with C4v and C6v symmetries as examples, and analyzed their coupling with the co-localized optical BICs and guided resonances due to both moving boundary and photo-elastic effects. We verified the theoretical analysis with numerical simulations of specific optomechanical crystals which support substantial optomechanical interactions between the mechanical BICs and optical resonances. Due to the unique features of high-Q, large-size mechanical BICs and substrate-enabled thermal dissipation, this architecture of slab-on-substrate optomechanical crystals might be useful for exploring macroscopic quantum mechanical physics and enabling new applications such as high-throughput sensing and free-space beam steering.

Segmentation and classification of two-channel C. elegans nucleus-labeled fluorescence images.

BACKGROUND: Aging is characterized by a gradual breakdown of cellular structures. Nuclear abnormality is a hallmark of progeria in human. Analysis of age-dependent nuclear morphological changes in Caenorhabditis elegans is of great value to aging research, and this calls for an automatic image processing method that is suitable for both normal and abnormal structures. RESULTS: Our image processing method consists of nuclear segmentation, feature extraction and classification. First, taking up the challenges of defining individual nuclei with fuzzy boundaries or in a clump, we developed an accurate nuclear segmentation method using fused two-channel images with seed-based cluster splitting and k-means algorithm, and achieved a high precision against the manual segmentation results. Next, we extracted three groups of nuclear features, among which five features were selected by minimum Redundancy Maximum Relevance (mRMR) for classifiers. After comparing the classification performances of several popular techniques, we identified that Random Forest, which achieved a mean class accuracy (MCA) of 98.69%, was the best classifier for our data set. Lastly, we demonstrated the method with two quantitative analyses of C. elegans nuclei, which led to the discovery of two possible longevity indicators. CONCLUSIONS: We produced an automatic image processing method for two-channel C. elegans nucleus-labeled fluorescence images. It frees biologists from segmenting and classifying the nuclei manually.

Cu-Catalyzed Cyanation of Indoles with Acetonitrile as a Cyano Source.

Cu-catalyzed cyanation of indoles with acetonitrile for the synthesis of 3-cyanoindoles has been developed. The Cu/TEMPO/(Me3Si)2 system has been identified to promote highly efficient and selective C-H cyanation of indoles by use of unactivated acetonitrile as a cyano source via a sequential iodination/cyanation process in one pot. This reaction furnishes 3-cyanoindoles in moderate to good yields and tolerates a series of functional groups. Moreover, low-cost copper catalysts and hazardless acetonitrile as a cyano source feature the practicability of this reaction.

Cesium carbonate catalyzed chemoselective hydrosilylation of aldehydes and ketones under solvent-free conditions.

Cs2CO3 has been found to be an efficient and chemoselective catalyst for reduction of aldehydes and ketones to alcohols with one equivalent of Ph2SiH2 as the reductant under solvent-free conditions. Most of the aldehydes employed can be effectively hydrosilated quantitatively to give the corresponding silyl ethers in 2 h at room temperature, whereas the hydrosilylation of ketones proceeded smoothly at 80 °C. The catalyst system tolerates a number of functional groups including halogen, alkoxyl, olefin, ester, nitro, cyano, and heteroaromatic groups; the selective hydrosilylation of aldehydes in the presence of ketone can be effectively controlled by temperature; and hydrosilylation of α,ß-unsaturated carbonyls resulted in the 1,2-addition products. The catalytic hydrosilylation of suitable dicarbonyls can be applied to the synthesis of poly(silyl ether)s with a high molecular weight and narrow molecular distribution.

[Analysis on medication rules of state medical master yan zhenghua's prescriptions that including Polygoni Multiflori Caulis based on data mining].

The prescriptions including Polygoni Multiflori Caulis that built by Pro. Yan were collected to build a database based on traditional Chinese medicine (TCM) inheritance assist system. The method of association rules with apriori algorithm was used to achieve frequency of single medicine, frequency of drug combinations, association rules between drugs and core drug combinations. The datamining results indicated that in the prescriptions that including Polygoni Multiflori Caulis, the highest frequency used drugs were parched Ziziphi Spinosae Semen, Ostreae Concha, Ossis Mastodi Fossilia, Salviae Miltiorrhizae Radix Et Rhizoma, Paeoniae Rubra Radix, and so on. The most frequent drug combinations were "Polygoni Multiflori Caulis-parched Ziziphi Spinosae Semen", "Ostreae Concha-Polygoni Multiflori Caulis", and "Polygoni Multiflori Caulis-Ossis Mastodi Fossilia". The drug association rules of confidence coefficient 1 were "Ostreae Concha-->Polygoni Multiflori Caulis", "Poria-->Polygoni Multiflori Caulis", "parched Ziziphi Spinosae Semen-->Polygoni Multiflori Caulis", and "Paeoniae Alba Radix-->Polygoni Multiflori Caulis". The core drug combinations in the treatment of insomnia were Ossis Mastodi Fossilia, Polygoni Multiflori Caulis, Salviae Miltiorrhizae Radix et Rhizoma, Ostreae Concha, Polygalae Radix, Margaritifera Concha, Poria, and parched Ziziphi Spinosae Semen. And the core drug combinations in the treatment of obstruction of Qi in chest were Salviae Miltiorrhizae Radix Et Rhizoma, Polygoni Multiflori Caulis, parched Ziziphi Spinosae Semen, Trichosanthis Fructus, Allii Macrostemonis Bulbus, and Paeoniae Rubra Radix.

Impact of Pediococcus acidilactici GLP06 supplementation on gut microbes and metabolites in adult beagles: a comparative analysis.

There is growing interest in the potential health benefits of probiotics for both humans and animals. The study aimed to investigate the effects of feeding the canine-derived probiotic Pediococcus acidilactici GLP06 to adult beagles by analysing the microbiome and metabolome. Twenty-four healthy adult beagles were randomly assigned to four groups. The CK group received a standard diet, while the three probiotic groups, the LG group (2 × 108 CFU/day/dog), MG group (2 × 109 CFU/day/dog), and HG group (2 × 1010 CFU/day/dog), received the standard diet supplemented with varying amounts of probiotics. The results show that, compared to the CK group, total antioxidant capacity was significantly increased in the MG and HG groups (p < 0.05), and superoxide dismutase and catalase were significantly increased in the HG group (p < 0.05). Compared to the CK group, malondialdehyde and blood urea nitrogen content were significantly decreased in the MG and HG groups (p < 0.05). Additionally, secretory immunoglobulin A activity was significantly increased in the HG group compared to the CK and LG groups (p < 0.05), and immunoglobulin G activity was significantly increased in the HG group compared to the CK, LG, and MG groups (p < 0.05). In addition, compared with the CK group, the abundance of Faecalitalea and Collinsella increased in the LG group, and the relative abundance of Tyzzerella and Parasutterella increased in the MG group. The α diversity and the relative abundances of beneficial bacteria (Faecalibacterium, Lachnospiraceae_NK4A1316, and Ruminococcaceae_UCG-005) were higher in the HG group than in the CK group. Furthermore, acetic acid content was significantly increased in the HG group compared to the CK, LG, and MG groups (p < 0.05). Butyric acid, isobutyric acid, and the total SCFA content were significantly increased in the HG group compared to the CK group (p < 0.05). Moreover, metabolome analysis revealed 111 upregulated and 171 downregulated metabolites in the HG group. In conclusion, this study presents evidence that supplementing with P. acidilactici GLP06 can have a positive impact on antioxidant activity, immunoproteins, SCFAs, and gut microbiota in adult beagles. These findings highlight the potential of probiotics as a dietary intervention to enhance gut health and overall wellbeing in companion animals.

Artificial heart valve reinforced with silk woven fabric and poly (ethylene glycol) diacrylate hydrogels composite.

The present study describes the preparation of woven silk fabric (WSF) and poly(ethylene glycol) diacrylate (PEGDA) hydrogel composite reinforced artificial heart valve (SPAHV). Interestingly, the longitudinal and latitudinal elastic modulus of the SPAHV composite can achieve at 54.08 ± 3.29 MPa and 23.96 ± 2.18 MPa, respectively, while its volume/mass swelling ratio and water permeability was 1.9 %/2.8 % and 3 mL/(cm2∙min), respectively, revealing remarkable anisotropic mechanical properties, low water swelling property and water permeability. The in vitro & in vivo biocompatibility and anti-calcification ability of SPAHV were further examined using L929 mouse fibroblasts and Sprague Dawley (SD) male rat model under 8 weeks of subcutaneous implantation. The expression of pro-inflammatory cytokine TNF-α and anti-inflammatory cytokine IL-10 was determined by immunohistochemical staining, as well as the H&E staining and alizarin red staining were accessed. The results showed that the composites possess better biocompatibility, resistance to degradation and anti-calcification ability compared to the control group (p < 0.05). Thus, the SPAHV composite with robust mechanical properties and biocompatibility has potential application for artificial heart valves.

Metabolomics and physio-chemical analyses of mulberry plants leaves response to manganese deficiency and toxicity reveal key metabolites and their pathways in manganese tolerance.

Introduction: Manganese (Mn) plays a pivotal role in plant growth and development. Aside aiding in plant growth and development, Mn as heavy metal (HM) can be toxic in soil when applied in excess. Morus alba is an economically significant plant, capable of adapting to a range of environmental conditions and possessing the potential for phytoremediation of contaminated soil by HMs. The mechanism by which M. alba tolerates Mn stresses remains obscure. Methods: In this study, Mn concentrations comprising sufficiency (0.15 mM), higher regimes (1.5 mM and 3 mM), and deficiency (0 mM and 0.03 mM), were applied to M. alba in pot treatment for 21 days to understand M. alba Mn tolerance. Mn stress effects on the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), intercellular CO2 concentration (Ci), chlorophyll content, plant morphological traits, enzymatic and non-enzymatic parameters were analyzed as well as metabolome signatures via non-targeted LC-MS technique. Results: Mn deficiency and toxicity decrease plant biomass, Pn, Ci, Gs, Tr, and chlorophyll content. Mn stresses induced a decline in the activities of catalase (CAT) and superoxide dismutase (SOD), while peroxidase (POD) activity, and leaf Mn content, increased. Soluble sugars, soluble proteins, malondialdehyde (MDA) and proline exhibited an elevation in Mn deficiency and toxicity concentrations. Metabolomic analysis indicates that Mn concentrations induced 1031 differentially expressed metabolites (DEMs), particularly amino acids, lipids, carbohydrates, benzene and derivatives and secondary metabolites. The DEMs are significantly enriched in alpha-linolenic acid metabolism, biosynthesis of unsaturated fatty acids, galactose metabolism, pantothenate and CoA biosynthesis, pentose phosphate pathway, carbon metabolism, etc. Discussion and conclusion: The upregulation of Galactinol, Myo-inositol, Jasmonic acid, L-aspartic acid, Coproporphyrin I, Trigonelline, Pantothenol, and Pantothenate and their significance in the metabolic pathways makes them Mn stress tolerance metabolites in M. alba. Our findings reveal the fundamental understanding of DEMs in M. alba's response to Mn nutrition and the metabolic mechanisms involved, which may hold potential significance for the advancement of M. alba genetic improvement initiatives and phytoremediation programs.

Corrigendum: Probiotic characteristics and whole-genome sequence analysis of Pediococcus acidilactici isolated from the feces of adult beagles.

[This corrects the article DOI: 10.3389/fmicb.2023.1179953.].

Effects of external field wavelength and solvation on the photophysical property and optical nonlinearity of 1,3-thiazolium-5-thiolates mesoionic compound.

The photophysical property and optical nonlinearity of an electronic push-pull mesoionic compound, 2-(4-trifluoromethophenyl)-3-methyl-4-(4-methoxyphenyl)-1,3-thiazole-5-thiolate, were theoretically investigated with a reliable computing strategy. The essence of the optical properties were then explored through a variety of wavefunction analysis methods, including the natural transition orbital analysis, hole-electron analysis, (hyper)polarizability density analysis, decomposition of the (hyper)polarizability contribution, and (hyper)polarizability tensor analysis, at the level of electronic structure. The influences of the electric field and solvation on the absorption spectrum and (hyper)polarizability of the molecule are highlighted and clarified. The results are expected to provide guidance for people to understand the effects of external field wavelength and solvation on the optical properties of mesoscopic molecules.