Molecular screening for pathogenic mutations in sudden cardiac death (SCD)-related genes is common practice for SCD cases. However, test results may lead to uncertainty because of the identification of variants of unknown significance (VUS) occurring in up to 70% of total identified variants due to a lack of experimental studies. Genetic variants affecting potential splice site variants are among the most difficult to interpret. The aim of this study was to examine rare intronic variants identified in the exonic flanking sequence to meet two main objectives: first, to validate that canonical intronic variants produce aberrant splicing; second, to determine whether rare intronic variants predicted as VUS may affect the splicing product. To achieve these objectives, 28 heart samples of cases of SCD carrying rare intronic variants were studied. Samples were analyzed using 85 SCD genes in custom panel sequencing. Our results showed that rare intronic variants affecting the most canonical splice sites displayed in 100% of cases that they would affect the splicing product, possibly causing aberrant isoforms. However, 25% of these cases (1/4) showed normal splicing, contradicting the in silico results. On the contrary, in silico results predicted an effect in 0% of cases, and experimental results showed >20% (3/14) unpredicted aberrant splicing. Thus, deep intron variants are likely predicted to not have an effect, which, based on our results, might be an underestimation of their effect and, therefore, of their pathogenicity classification and family members’ follow-up. Unexpected sudden deaths remain a significant challenge to healthcare systems and forensic examinations worldwide. Sudden deaths can be classified as sudden cardiac death (SCD) when SD has a cardiac primary origin or as SD from non-cardiac origin. In SCD cases, molecular screening for pathogenic mutations in SCD-related genes is common practice .Previous studies have been performed to genetically analyze SCD cohort in Catalonia during the last 10 years ,3. ThoseGenetic variants affecting potential splice site variants are among the most difficult to interpret. Mutations which affect splicing are significant contributors to rare disease but are frequently overlooked by diagnostic sequencing pipelines. Splicing consensus regions are defined between positions 4 to 1 for acceptor site and from +1 to +6 for donor site. Thus, potential splice sites can be divided into three groups: canonical acceptor site variants (4 to 1), canonical donor site in position (+1 to +6), and deep intron variants (within the intron but outside the consensus sequence). However, the major consensus nucleotides at the U2 spliceosome donor and acceptor sites are GT and AG, which are known as the most classical canonical positions .At least 20% of SCD are due to rare hereditary cardiac diseases, and the genetic evaluation relies on rare coding and intronic flanking regions . HoweverThe aim of this study was to examine rare intronic variants identified in the exonic flanking sequence to meet two main objectives: first, to validate that canonical intronic variants produce aberrant splicing; second, to determine whether rare intronic variants predicted as VUS may affect the splicing product. To achieve these objectives, 28 heart samples of cases of SCD carrying rare intronic variants were studied.SCN5A_c.1862del and Case #21 TNNT2_c.832C>T). The remaining 26 cases only carried VUS  and +3 to +6 (donor site). These types of variants are considered the most classical mutations in the canonical sites [AG/G sequence [The most classical mutations in the canonical acceptor sites are considered 1 to 2, affecting the NYsequence . In our GUAAGU [The most classical mutations in the canonical donor sites are considered +1 to +2, affecting CAG/GUAAGU . In our Experimental results of cDNA sequencing confirmed aberrant splicing product in both cases. MYPN_c.2703+1G>T exon 12 skipping and TGFBR3_c.568+1G>A showed exon 6 skipping in heterozygosis, as predicted . In bothIn the canonical sequence, beyond positions +/−1 and 2, we identified 10 other mutations: 3 in the acceptor site and 10 in the donor site. All of them were predicted to have no effect on the splicing product by in silico platforms .MYH6_c.3343-3C>A, TNNT2_c.690-4G>T and FLNC_c.5843-4C>T. In all cases, the results of the splicing product sequencing confirmed no aberrant forms supporting the in silico predictions.The three mutations identified in the acceptor site sequence in positions 3 and 4 were AAGU). Interestingly, from these seven variants, one variant TTN c.3224+5A>G produced unpredicted aberrant splicing product excluding exon 161 . Among these variants, a particular case was found. ANK2_c.3224+7G>A was located in the 2728 intron. Although exon 28 was reported to be expressed in the heart, both the carrier and noncarrier control the same splicing product with the exclusion of exon 28  with the inclusion of an in-frame PTC , in silico programs predicted an effect in 100% of cases (4/4). On the contrary, none of the canonical site variants beyond +/−1 and 2 positions were predicted to affect splicing product (0/10). Experimental data showed aberrant product in 75% of the most canonical variants (3/4) while none of the remaining canonical site variants produced aberrant splicing product, supporting the in silico prediction. On the other hand, for deep intron variants, three aberrant splicing products were identified (3/14). All of them were unpredicted by the in silico programs. Thus, in this study, the in silico predictions for deep intron variants showed 0% sensibility and 83.3% specificity. Taking all data together, the overall accuracy of in silico predictors was determined to be 89.3% with a lower value for deep intron variants (78.6%) .MYH6 gene, which encodes for the alpha heavy chain subunit of cardiac myosin, showed aberrant splicing consistent with the predicted donor loss in the splicing consensus region. This aberrant splicing product led to a PTC which would presumably trigger the nonsense-mediated decay (NMD) machinery resulting in the degradation of the allele. Thus, this variant would be expected to cause MYH6 haploinsufficiency, but our results also showed undetectable wild type cDNA, suggesting a possible unexpected phenomenon of monoallelic expression.Firstly, c.2051-2del variant in TGFBR3 c.568+1G>A, which encodes for transforming growth factor beta receptor 3 which has not been defined as definitive in any SCD-related disease, was proved to lead to a PTC triggering NMD. Lastly, our study identified MYPN c.2703+1G>T in a case of SCD. This variant was predicted to cause donor loss in the splicing consensus regions which would lead to exon 12 skipping as was confirmed by our sequencing results, leading to a PTC p.(Gly777Phefs*38). Therefore, this variant would cause haploinsufficiency for MYPN. In this case, the circumstances of death are compatible with an SCD event . The carrier suffered a sudden cardiac death with no structural alterations being defined in the autopsy as a death of arrhythmogenic origin. Furthermore, this case also carried a likely pathogenic variant in SCN5A leading to a PTC.TTN_c.301796_30179-5insG was found to produce a PTC p.(Pro10086_Lys10087ins28*). In this case, the patient was a 24-year-old female who suffered an SCD event with a possible toxicological status and did not carry any other LP variation. No structural phenotype was reported in the autopsy.Finally, In sudden death cases, molecular screening for pathogenic mutations in SCD-related genes is common practice. However, genetic test results are sometimes challenging to interpret due to uncertainty because of the identification of VUS in the concurrent absence of clearly pathogenic mutations. In this sense, intronic variants are very challenging to interpret and very frequently classified as VUS in the absence of experimental data.To tackle this challenge, the aim of this study was to elucidate the functional effect of potential splice site variants in 28 cases of sudden cardiac death and evaluate whether there are discrepancies between computational predictions and experimental evidence.The results in our cohort show that consensus donor splice site variants are more prevalent than acceptor splice site variants. Our study presents a ratio of 1.8:1 in concordance with previous knowledge in other fields and based on larger previous studies describing a ratio of 1.5:1 .Our results show 86.95% of the genetic variants predicted not to affect splice sites do not show any aberrant splicing form of mRNA, supporting the in silico prediction. On the other hand, only 60% of genetic variants predicted to highly affect splice sites have been confirmed experimentally to show an aberrant splicing product. Additionally, unpredicted aberrant splicing products were identified in around 10% of the total variants, suggesting that in silico predictions may sometimes underestimate effects of intronic variants, especially those variants not affecting the most classical canonical splicing site (1/2 and +1/2). All unexpected aberrant splicing products have been found either in deep intron variants or canonical variants beyond positions +1/2 or 1/2.Interestingly, in our study, canonical splicing sites show much higher accuracy, sensitivity and specificity than deep intron variants. Our results set sensibility of canonical variants at 75% and specificity at 90%. In concordance with previous publications, splice site prediction tools have higher sensitivity relative to specificity in predicting splice site abnormalities ,9.Importantly, our results also suggest that intronic variants affecting the most classical canonical site (+/−1 and 2) are mostly predicted to have an effect (100%), while variants affecting canonical site from −3 to 4 and +3 to +6 are generally predicted not to affect splicing product (0%). In our study, experimental data showed that the classical canonical site (+/−1 and 2) led to aberrant splicing in 75% of cases, overestimating their effect, while canonical variants beyond +/−1 and 2 may be underestimated.In this sense, deep intron variants showed no sensibility in our study; none of the abnormal splicing products detected were predicted by in silico tools while the only one predicted to have a moderate effect revealed a normal splicing product. These results suggest that deep intron variant predictions have very low sensitivity which might lead to an underestimation of the effect of these kinds of variants when classifying their pathogenicity. Thus, experimental results of splicing product sequencing showed that there is more complexity in the interpretation of rare intronic variants.TRDN c.1322-10T>A, MYPN c.2703+1G>T and TTN_c.301796_30179-5insG should at least be taken into account in further cases while the remaining three  did not show sufficient evidence to be considered the potential genetic cause.Our study showed six aberrant splice products, three with unpredicted effects. In terms of their possible causality, taking the experimental results, autopsy details and previous literature together, we believe that MYPN c.2703+1G>T leads to a PTC p.(Gly777Phefs*38), and therefore this variant would cause haploinsufficiency for MYPN. MYPN has been described to be associated with both hypertrophic and dilated cardiomyopathy (DCM) [TRDN c.1322-10T>A located in TRDN encodes Triadin, a protein important for calcium release regulation from the sarcoplasmic reticulum. Genetic variants in TRDN have been widely reported to be the cause of the CPVT phenotype [TTN_c.301796_301795insG was found to produce a PTC p.(Pro10086_Lys10087ins28*). Loss of function variants in TTN has been considered to be pathogenic in the context of DCM [TTN_c.301796_30179-5insG may be related to SCD.hy (DCM) , althougt of DCM . Thus, wTGFBR3 c.568+1G>A would lead to a PTC triggering NMD, the circumstances of death showing possible myocardial infarction in the autopsy and this gene has been associated with Marfan syndrome in a single publication, though there is limited evidence to support this gene disease association [TTN c.3224+5A>G was found to produce exon skipping, leading to an in-frame deletion in the translated protein. However, in this case the patient also carried a likely pathogenic variant in SCN5A leading to a PTC, which may be a stronger candidate as the causal mutation. The contribution of TTN c.3224+5A>G in the SCD event remains unknown, as well as the effect of this variant when identified solely.On the other hand, MYH6 has limited evidence to support this gene disease relationship . In addiociation . FinallyTaking all of the above together, our data showed that in silico predictors alone are insufficiently reliable to determine the effect of splicing variants. Our study revealed some unexpected aberrant splicing products. Cardiac samples from SCD cases are very difficult to obtain and highly valuable to functionally evaluating genetic variants. We strongly suggest that, when possible, experimental data should be assessed as they are crucial to elucidating the role of intronic variants, and this could make the difference to properly evaluating the risk. Additionally, correlation with forensic information is key to the proper interpretation of genetic variants in terms of SCD outcome.This study has some limitations that should be mentioned. Firstly, the cohort size was limited in extrapolating the accuracy of in silico predictors. It is very challenging to find SCD cases carrying rare intronic variants with heart samples available to study the splicing products, and therefore experimental data may be valuable for future variant interpretations. Secondly, the distribution of variants among groups is heterogeneous because of the stochastic nature of genetic variant appearance. Third, the Sanger sequencing technique does not have the capability to detect sequences representing less than 5% of the total products. Thus, we cannot discard that all variants showing only the normal splicing isoform might be causing an aberrant isoform with less than 5% of relative expression.The present study was designed as a part of the MOSCAT project which encompasses the genetic study of all of sudden death (SD) suffered by individuals younger than 50 years old occurring in Catalonia (Spain) from 2012 to 2020. This study included the collection of heart samples of all cases of SD with a mandatory judicial autopsy occurring in Catalonia. The study was approved by the ethical committee of Hospital Universitari Dr. Josep Trueta de Girona (Spain) and conformed to the ethical guidelines of the Declaration of Helsinki 2008.Forensic autopsies were performed to determine the cause of death. This forensic autopsy included an exhaustive histologic and macroscopic cardiac exploration including histological tissue analyses, as well as toxicological investigation. In most cases, different parts of the heart were collected and frozen for future functional and molecular studies.Genetic analysis was performed in all individuals fulfilling inclusion criteria according to the flow chart  which inAll variants with a minor allele frequency (MAF) < 0.1% in PopMax Filtered in gnomAD were selected to be confirmed with the conventional Sanger technique. From filtered variants confirmed by Sanger sequencing, we selected all cases carrying intronic variants within the flanking region covered by the custom NGS panel (within +/−25 pb). Maxscore and SpliceA software programs were used to predict splicing effects. In addition, the Human Gene Mutation Database (HGMD) and PubMed were used to ascertain previously reported pathogenic mutations. Finally, all the variants were classified as pathogenic (P), likely pathogenic (LP) or variants of unknown significance (VUS) according to the standards and guidelines for the interpretation of sequence variants from the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. All variants are described according to the last version 20.02 of HGVS released 1 May 2020.Cardiac samples were stored at −80 °C from their initial collection until their processing (January–March 2022), with no prior freeze–thaw cycles. Total RNA was isolated from left ventricle heart tissue. A total of 25mg of frozen tissue was processed per sample. Tissues were disrupted and simultaneously homogenized by agitation in the presence of beads and lysis buffer in Tissuelyser LT  for 2 min at 30 Hz. RNA was extracted using the RNeasy Mini Kit  according to the manufacturer’s instructions. This protocol includes incubation of Proteinase K at 55 C for 10 min. All 28 cases suffered SCD in the period 2016–2021. Prior reverse transcription reaction was performed with an additional step of DNase I treatment and with gDNA Wipeout buffer. Reverse transcription reactions of RNA were performed using the QuantiTect Reverse Transcription Kit . For each 20 µL reverse transcription reaction, 1 µg of total RNA was mixed with 4 µL of RT buffer, 1 µL of primer mix and 1 µL of Reverse Transcriptase in nuclease-free water. The cDNA concentration and 260/280 ratio were checked using a NanoDrop1000 spectrophotometer .® Terminator v3.1 Cycle Sequencing Kit . Sequencing was processed in a 3500 Genetic Analyzer  and analyzed by means of the Sequencing Analyzer Software  comparing obtained results with the reference sequence from hg19.cDNA was analyzed using Sanger sequencing. Firstly, polymerase chain reaction (PCR) was used to amplify the interest regions. Primers were designed in coding regions of the nearby exons with amplicon size 100–250 pb. The PCR product was purified by ExoSAP-IT  and directly sequenced using the dideoxy chain termination method in ABI Prism Big DyeOur results showed that rare intronic variants affecting the most canonical splice sites displayed in 100% of cases that they would affect the splicing product, possibly causing aberrant isoforms. However, 25% of these cases (1/4) showed normal splicing, contradicting the in silico results. On the contrary, in silico results predicted an effect in 0% of cases, and experimental results showed >20% (3/14) unpredicted aberrant splicing. Thus, deep intron variants are likely predicted to not have an effect, which, based on our results, might be an underestimation of their effect and, therefore, of their pathogenicity classification and family members’ follow-up.


Importantly, theparticle size of selected Fe catalysts will ultimately affect thebasic heating properties of the catalysts and decisively influencetheir catalytic performance under microwave initiation. In addition,we have found that when two or more materials—present as amechanical mixture—are simultaneously exposed to microwaveirradiation, each constituent material will respond to the microwavesindependently. Thus, the interaction between the two materials hasbeen found to have synergistic effects, subsequently contributingto heating and improving the overall catalytic performance.Knowledge of theelectromagnetic microwave radiation–solidmatter interaction and ensuing mechanisms at active catalytic siteswill enable a deeper understanding of microwave-initiated chemicalinteractions and processes, and will lead to further optimizationof this class of heterogeneous catalysis. Here, we study the fundamentalmechanism of the interaction between microwave radiation and solidFe catalysts and the deep dehydrogenation of a model hydrocarbon,hexadecane. We find that the size-dependent electronic transitionof particulate Fe metal from a microwave “reflector”to a microwave “absorber” lies at the heart of efficientmetal catalysis in these heterogeneous processes. In this regard,the optimal particle size of a Fe metal catalyst for highly effectivemicrowave-initiated dehydrogenation reactions is approximately 80–120nm, and the catalytic performance is strongly dependent on the ratioof the mean radius of Fe particles to the microwave skin depth ( Goodenough’sseminal contributions span not onlyhis pioneering work with colleagues at Oxford on lithium-ion batteries,but also his profound influence on our current understanding of thebehavior of localized versus delocalized electrons in solids, particularlyin the varied roles of d electrons and the associated phenomenon ofthe metal-to-insulator transition (MIT). There are countless examplesin macroscopic systems and materials whereby relatively small changesin thermodynamic parameters and the resulting electrical conductivity can change by many ordersof magnitude as a system transforms from a metallic to a nonmetallicregime across the MIT. Of course, one classic example is the caseof VOWe highlighthere also the intriguing possibility of a metal-to-insulatortransition driven solely by the physical dimensions of a metallic particle. Thus, the inevitable consequence of the successivefragmentation of a metallic particle must be the ultimate cessationof conducting behavior within a mesoscopic or microscopic particleof a critical size. This is the size-induced metal–insulatortransition (SIMIT). It is important to note that such an electronicphase transition is driven purely by the physical dimensions of anindividual particle. Here, we illustrate that small particles of Feand Ni catalysts with dimensions characteristic of the SIMIT are efficaciousat harvesting microwave energy and converting it into heat. This phenomenonhas the desirable effect of maximizing microwave-initiated local heatgeneration at the active site and significantly enhancing the particletemperature and, with that, the catalytic activity of particles closeto the SIMIT. We believe that this phenomenon beautifully highlightsJohn Goodenough’s pioneering approach to the science and technologyof materials where several disciplines—here, catalytic chemistry,condensed matter physics, and microwave science and engineering—areintimately related and naturally united in modern multidisciplinaryresearch.12 However, microwave heating effectson solid state compounds and mixtures are highly complex and are stillnot fully understood. The ability of microwaves to directly transferenergy and activate specific bond activation via a catalyst, whilenot significantly heating a surrounding substrate ,can be used to alter the thermodynamics of chemical reactions andprocesses in much the same way as we have traditionally used temperatureand pressure and thus can affect catalytic activity and selectivity.Microwave heating hasmany advantages over conventional heating,centering on noncontact, selective and rapid heating, and quick start-upand shutdown. The incoming microwaves can be transported from thesource through a transparent, quartz, or hollow nonmagnetic metaltube to the sample.4 These can include rotational polarization of dipolar molecules,such as water, charge transport, and interfacial polarization in solidsknown as Maxwell–Wagner polarization.4Microwave dielectric heating requires candidate dielectric materialsto convert incoming electromagnetic energy to heat thus allowing catalyststo drive reactions under microwave initiation. Several different mechanismsin the interaction, for example, between the electric field of theelectromagnetic radiation and materials, can initiate the resultingheating of microwave-responsive molecules and materials.2-free hydrogen production from hydrocarbons.5 As the incoming microwave radiation interactsselectively with only the catalytic particles while the hydrocarbonsubstrates typically remain much colder due to their lack of absorptionof electromagnetic radiation, many competing side reactions, includingthe self-decomposition of hydrocarbons, are significantly reduced.This fundamentally different interaction between microwave radiationand materials will naturally create a temperature gradient betweenthe active catalyst and the substrate or support, and this gradientwill enhance the molecular diffusion from, and heat transfer within,the sample.6 However, it appears to be of great importanceto select a catalyst for microwave-initiated reactions which meetsspecific requirements. These are in addition to the necessary highactivity, selectivity, and stability required of operating catalysts,and such a catalyst must be a good microwave susceptor and be ableto retain its structure and properties under intense microwave irradiation.8 In general, metal- and carbon-based catalysts have been widely used.As a resultof the many advantages of microwave-initiated catalysisover conventional thermal processes, such as enhanced energy efficiency,higher heating rates, higher reaction rates, and better product selectivityand yield, microwave technology has recently been applied to the importantprocess of CO9 which showan excellent ability to absorb microwaves, and because of this carbonmaterials are commonly used as microwave susceptors which heat othermaterials indirectly, or they themselves directly act as a catalystin different heterogeneous reactions. A variety of carbon materials,such as activated carbons, metallurgical cokes, chars, or anthracite,were used for several microwave-enhanced heterogeneous catalytic reactions.9 Domínguez et al. investigated the microwave-assisteddecomposition of methane on activated carbon, which produced a higherselectivity of H2 and higher conversions compared to electricalor conventional heating.10 The improvedcatalytic performance was attributed to the formation of hot spotsinside the catalyst bed which favor CH4 decomposition.Jie et al.11 studied various carbon materialsand residues with different geometries and structures and examinedtheir initial interaction and catalytic performance when used in dehydrogenationreactions under microwave irradiation. However, even though all thetested carbon materials displayed excellent microwave absorption properties,only a few types of carbonaceous materials, such as activated carbonsand graphene nanoplatelets, appeared to be catalytically active forthe microwave-initiated dehydrogenation of hexadecane.Ménéndez et al. reported on microwave heating processesinvolving carbon materials,14 The tetralinconversion was significantly enhanced from 31% in conventional thermalheating to 56% under microwave irradiation.14 This enhancement was explained by the highly effective heating abilityof Pt/carbon particles which created a large-temperature gradientbetween the catalyst and the tetralin solution under microwave conditions.Horikoshi et al.12 achieved over 94% conversionof methylcyclohexane using a Pd/AC catalyst at 340 °C in 2 min.In studieson metal catalysts in microwave-initiated heterogeneouscatalysis, Suttisawat and Horikoshi et al. showed efficient hydrogenproduction from the dehydrogenation of various organic hydrides, includingmethylcyclohexane, tetralin, and decalin, over carbon-supported Ptand Pd catalysts.15 proposed using long-chain alkanes, such as paraffin wax , as a benign hydrogen storage material; it wasdemonstrated that the rapid liberation of hydrogen could be achievedvia microwave-initiated catalysis of the paraffin wax. A ruthenium(Ru/AC) catalyst on an activated carbon support was prepared and usedfor hydrogen production using paraffin wax (C26H54) decomposition under microwave irradiation. A hydrogen concentrationof 60–80 mol % was obtained in the exit gas stream over theRu/AC catalyst. In contrast, only approximately 40 mol % of hydrogenwas produced when only an activated carbon catalyst, without the rutheniummetal, was used. The authors attributed this to the large availabilityof surfaces of the activated ruthenium metal nanoparticles.15 Jie et al.18 used iron, nickel, andalloys of these metals supported on silicon carbide (SiC) as catalyststo dehydrogenate fossil hydrocarbons to produce high-purity hydrogenunder microwave irradiation. A very high selectivity for H2 production, 98% of all evolved gases, was achieved; this was muchhigher than using conventional thermal processes. In addition, theauthors noted that the catalytic performance under microwave irradiationwas varied by using different metals, support materials, and metalloadings.Research by Gonzalez-Cortes et al.20 Of these products there was mainlyhydrogen, ethylene, and α-olefins present in the liquid products.The content of α-olefins was more than an order of magnitudegreater than the content of other products, mostly alkanes. They associatedthe high α-olefin selectivity to the spark discharge that aroseon the carbon surface upon microwave irradiation; this caused C–Cor C–H bond cleavage to form alkyl radicals and hydrogen atomsin a short reaction time period.20 However,Udalov et al. argued that the exclusive selectivity of hexadecanepyrolysis to hydrogen, ethylene, and α-olefins might also bea consequence of the catalytic action of a variety of naturally occurringmetals contained within the carbon. This was supported by the proposalthat metallic catalysts under microwave irradiation involve hot spotswhich promote the thermal reactions of methane, which leads to theformation of gas-phase methyl radicals and hydrogen atoms.21 Therefore, an expanding range of catalysts,including Fe2O3, magnetic microspheres , glass fibersupported palladium catalysts, metal-ceramic Al2O3/Al catalysts, ZSM-12 zeolite catalysts, and 70% ZSM-5/Al2O3 (0.2–1.0 mm fraction), were investigated formicrowave-assisted hexadecane pyrolysis. As a result, methane, ethylene,and propylene were found to predominate in the gaseous reaction products,and similarly, α-olefins were mostly observed in the liquidproducts of the hexadecane pyrolysis when using magnetic microspheresand metal-ceramics.21 These results againindicate the great importance of choosing an appropriate catalystfor microwave-initiated catalysis.The difference between carbon-based and metal-basedcatalytic systemsfor microwave-initiated catalysis has also been studied by Tanneret al., who reported on the microwave-assisted catalytic reactionsof a variety of liquid hydrocarbons  using millimeter-sized chars. A vigorous emissionof sparks was generated over the chars while under microwave irradiationand resulted in molecular hydrogen, gaseous hydrocarbons, and a rangeof liquid olefins.With a better understandingof an active catalyst’s interactionswith microwave radiation, we can more effectively and specificallyoptimize its catalytic performance. Here, we studied the importanteffect of the particle size of metal catalysts and the initial interactionof two or more materials/substances under microwaves; in all cases,the temperature profile and microwave energy absorption changes weremonitored. The corresponding catalytic performance of using differentsized Fe particles, a mixture of two or more materials, and differentsupporting materials for the metal catalysts were also investigated,and the results are presented here.22.1The different sized ironparticle powders, including 25 nm, 35–45 nm, 60–80 nm,200 mesh (74 μm), 70 mesh (210 μm), and 20 mesh (841 μm)iron particles, and activated carbon (AC) were bought from Sigma-Aldrichand used as purchased without further treatment. The mixture sampleof iron and activated carbon was prepared by physically mixing a certainamount of iron particles and activated carbon, and the mixture wasthen vigorously blended using a pestle and mortar.3)3·9H2O (iron(III)nitrate nonahydrate, Sigma-Aldrich), and nickel nitrate, Ni(NO3)2·6H2O (nickel(II)nitrate hexahydrate, Sigma-Aldrich), were used as metal precursors.AC  and SiC , of the SiC–6H structure, were used as supportingmaterials. In the preparation, the supporting material was mixed withan aqueous solution of metal nitrate, the concentration of which wascalculated to produce the desired metal loading. The mixture was stirredat 150 °C for 3 h on a magnetic hot plate until it became a slurry.The slurry was then moved into a drying oven and left overnight. Theresulting solid mixtures were calcined in a furnace at 350 °Cfor 3 h. Finally, the active catalysts were obtained by a reductionprocess in 10% H2/argon gases at 800 °C for 6 h.17The AC andsilicon carbide (SiC) supported metal catalysts were prepared usingthe so-called incipient wetness impregnation method. Iron nitrate,Fe electric fields in the purpose-built aluminum cavity.The samples were first purged using an Ar flow at a rate of 1.67 mL·s–1 for a period of 15 min. The samples were then irradiatedwith microwave irradiation at different input powers for 10 min. Thesample temperature was recorded using an infrared (IR) pyrometer,which was also used to control the power of the generator. A Labviewsoftware program was linked to control the microwave system, and thetemperature (T), input power (W), and dissipatedpower (W) versus time (t) profiles were recordedwith this program.The temperatureprofile and delivered MW power of materials undermicrowave irradiation were recorded by exposing the samples to differentmicrowave power. The experimental setup was reported previously andconsists of a microwave generation system, a purpose-built microwavecavity, and a control system.2.3010 microwave cavity to minimize depolarization effects undermicrowave irradiation. Before the microwave generator was started,the samples were purged with an Ar flow at a 1.67 mL·s–1 rate for a period of 15 min. The sample was then irradiated withmicrowaves for 10 min at an input power of 750 W. The evolved gasproducts were collected and analyzed using a gas chromatographer . The unreacted “escaped”hydrocarbon feedstocks were recycled, and their composition was confirmedby a gas chromatograph mass spectrometer .The material catalytic activity tests were carried outusing thesame experimental setup and quartz tube as discussed in the microwaveresponse test. In addition to the sample preparation, a certain amountof hexadecane  was mixed/injected into the tube and left for 5–10 minuntil the liquid hexadecane was well dispersed into the catalyst bed.The filled tube was then placed axially in the center of the TMVp is the volume % ofone gas product obtained from gas chromatography(GC), and ∑V(Pi) is the sum of the volume % of all the productsin the exit gases.We determined the catalytic performance of a material sampleunder microwave irradiation as the hydrogen production in terms ofthe hydrogen concentration in the evolved gas products. The selectivitytoward different gaseous products was evaluated in terms of the volume% of the product composition in the exit gases that had been analyzedby GC 1.1Vp is 33.13.1.122 first reported a drastic decrease in electrical conductivity withparticle diameter below a few micrometers; in later years, Edwardset al.23 proposed that by varying the sizeof the individual mesoscopic particles, any value of their conductivitycan be adjusted between the full extremes of an insulator and a metalbelow that of the corresponding bulk metal. This is known as the size-inducedmetal–insulator transition (SIMIT) and forms the fundamentalphysical basis for the possible transition of metals from a “reflector”of microwave irradiation to an “absorber” in the mesoscopicregime.Unlikehigh dielectric loss factor materials  that can efficientlyabsorb microwaves, bulk metals are themselves impenetrable to microwaves(beyond their characteristic skin depth), primarily owing to the presenceof an itinerant, free-electron cloud which causes broad-band reflectionat microwave frequencies. Thus, bulk metals are usually reflectorsof microwaves. In 1988, Gleiter et al.24In Arising from such a SIMIT, Feparticles on the nanoscale achievednoticeably higher temperatures than those on the meso- or microscale.The largest of the Fe particles, 841 μm, heated to approximately120–140 °C at various microwave input powers, while thetemperature achieved by the 60–80 nm sized Fe particles wasalways approximately 100 °C higher. However, we note that thetemperature of the Fe particles was not a linear function with respectto the particle size 3c. On the of its power value at the surface.f is the frequency. Thus, for anyconductor like iron with high permeability and conductivity, the skindepth is very small, usually between the nanoscale and microscalefor a GHz frequency.26The temperatureprofiles of the different sized Fe particles reflectthe sample’s microwave-absorbing properties because the heatis generated by the conversion of absorbed electromagnetic energy.In the interaction of microwaves and metal particles, the skin depthof the sample material must be carefully considered; the skin depth(δ) describes the distance at which the microwave power decreasesto 1/27 calculated electromagneticabsorption in small conducting particles within microwave fields fora range of particle sizes and conductivities. It was concluded thatthe magnetic absorption dominates electrical absorption over a widerange of radii for highly conducting particles with an optimum absorptionset by the ratio of the mean particle radius to its skin depth (r/δ). This indicates that for metal particles of anyconductivity, optimized magnetic absorption, and hence microwave heatingby magnetic induction, can be achieved by the simple selection ofthe mean particle size.Porch et al.28 Thus, the volumeof the Fe particle, which absorbs incoming microwave power, is closelyrelated to its particle size and skin depth (r < δ), thefull volume of the particle will absorb the microwave radiation andgenerate heat. However, on the nanoscale of the tested Fe samples,smaller particle sizes of Fe produced lower temperatures. This isbecause as the particle’s size is increased, a greater volumeof material will present itself to absorb the microwaves until theradius becomes larger than the skin depth. This again demonstratesthe importance of the ratio of the mean particle radius and the skindepth (r/δ),27 whichwill affect the heating properties of Fe particles under microwaveirradiation. In contrast, on the microscale, the temperature reachedby Fe particles decreased as the particle size increased; this isnot only because at the macroscopic level the Fe metal particles willalso exhibit conducting behavior that reflects microwaves withoutheating but also because the fraction of the particle’s volumethat is available to absorb electromagnetic energy is smaller in largeFe particles and therefore presents poor heating.In the experimental demonstration, weshowed that the temperatureachieved among different sized Fe particles was 80–60 nm >45–30 nm > 25 nm > 74 μm > 210 μm >841 μm1 and 3c.in depth 2. When tConventional heating is a slowprocess—particularly fora heterogeneous mix of a metal catalyst particle + a low  absorption hydrocarbon —necessitatingthe conduction of heat from the exterior surface of the mixture tothe interior to ultimately reach the catalyst particle. In contrast,microwave heating is more efficient; it is driven by the direct absorptionand transfer of microwave energy within the interior of the heterogeneousmixture. Hence, incoming electromagnetic energy is directly transferredto the catalyst particle without depending on such a heat transferprocess. Within this study, the Fe particles were heated within 30–120s and stabilized at the relevant temperatures. This can be seen fromthe plateau on the graphs, at which a balanced/equilibrated heat/energyenvironment was built up 1. Thus, minus thereflected power to illustrate the evolved change of microwave powersthat were delivered to the cavity. In relation to the wave impedancematching, the change of the sample’s permeability, permittivity,physical dimensions, and temperature can affect the actual amountof microwave power delivered to the cavity.We note that in this study, “deliveredMW power”was taken from the microwave input power As a general observation,both the temperature of the samples andthe delivered MW power in the plateau region of the graphs are almostlinearly increased when using a higher microwave input power 3a and b.r/δ)is below 1, on the nanoscale, smaller particles produced less heat;at the Fe particle size of 60–80 nm, where the r/δ ratio is approximately 1, the highest temperature amongall the tested samples was reached.In r/δ>1) were barely heatedunder exposure to microwaves becausethese large particles were not fully penetrated by microwave irradiation.Interestingly, the delivered MW power remained almost constant forall the different sized particles, suggesting that it is independentof Fe particle size. However, the samples containing the smallestFe particles, of characteristic size 25 nm, reflected the most microwaves.Therefore, for metal particles exposed to microwaves, the optimumparticle size for heating is approximately 2–3 times that ofthe material’s skin depth, and the optimum absorption is determinedby the ratio of the mean particle radius to the skin depth (r/δ). With this knowledge, particle size can be carefullyvaried (“tuned”) to achieve more efficient heating.In contrast, the micrometer-sizedFe particles  in a weight ratio of 1:1. The mixture sampleswere then tested under different microwave power inputs.In microwave-initiated heterogeneouscatalysis,In Importantly, the observed temperature of the 841 μm Fe andAC mixture was approximately 100–200 °C higher than thatof their constituent (separated) samples. However, interestingly,there were few differences found in the delivered microwave power:particularly, the delivered microwave power of the mixture, whichis nearly the same as that of the pure Fe particles. To make a comparisonof this discovery between the physically mixed materials and the microwaveinput power, we then collected the point data at 600 s, which we takeas the balanced heat/energy stage, and these data are given in 18 presented thatthe electric field strength and the heating rate at the interfaceof the two substances increased significantly due to interfacial polarization.High localized electric fields and increased heating rate will occurbetween the particle surfaces.27For particles at the nanoscale, compared to boththe Fe particlesand the AC powder alone, the temperature was mildly increased whenboth materials were mixed 5a. In coMoreover, despite the increased microwave input power supply, thedelivered MW powers of two Fe particles sizes, one 60–80 nmand the other 841 μm, and their mixture with AC were nearlythe same 5b.This Thus, wherethe particle size of both Fe particles exceeds thevalue of its characteristic skin depth, they primarily reflect themicrowaves. One can imagine that not only will a large metal particlehave increased electrical conductivity which increases the reflectivityto microwaves, but also the interior core of the metal particle willremain cold; this is a result of the limited microwave penetrationand energy absorption which cannot heat up the entire particle 2. Import33 the combination of plasma and solid metal particles under microwaveirradiation has been found to have synergistic effects and enhancethe average electric field strength.33 Surfaceabsorption within a plasma volume can also make a significant contributionto heating.18 Unfortunately, we note thatit is difficult with current characterization techniques to distinguishthe difference between the synergistic effect by surface interfacialpolarization and the plasma effect. Further studies that take intoaccount the interfacial chemistry and nonequilibrium kinetics undera microwave electric field need to be undertaken, and we are currentlyaddressing this issue.Despitealmost the same delivered MW powers among the Fe particlesand the mixture of Fe and AC, higher temperatures were observed forthe mechanical mixture samples. This indicates that the synergisticeffect from surface interfacial polarization of two constituent substances,under microwave irradiation, will generate heat. Furthermore, nonequilibriumplasma could potentially be generated at the interface of the twosubstances, initiated by the microwave irradiation;3.1.3To further study the combination of two solid substancesat a close physical contact/proximity, under microwave initiation,we prepared activated carbon (AC) and silicon carbide (SiC) supportedmetal catalysts. Iron and nickel metal particles were loaded throughan incipient wetness impregnation method  particles and the Fe particles under microwave irradiationis over 500 °C. We believe the proximal contact of iron particlesand SiC support causes synergistic surface effects leading the supportedmetal catalysts to exhibit heating properties above that of the independentconstituent material. Moreover, the delivered MW power increased significantly. With theburgeoning interest in clean hydrogen production, ideally with noCO2-free hydrogenproduction from hydrocarbons can be identified. The first is the efficientenergy transfer from the incoming microwaves to the catalyst particlesenabling rapid heating on the particle surface, where the initiationof the catalytic reaction also occurs. The second important advanceis the apparent, effective limitation or inhibition of side reactionsof self-decomposition of hydrocarbons which would occur at highertemperatures. Under microwave-initiated conditions, hydrocarbons areessentially transparent to microwave irradiation, and the “bath”will initially remain cold before contacting the hot catalyst particles.As a preferred mechanism of the microwave-initiated process, catalyticscission of chemical C–H bonds in hydrocarbons18 significantly improves the selectivity to H2 and hence narrows the chemical product distribution.Two advances in utilizing microwaves for CO2 and solid carbon with a smallamount of methane, ethylene, and C2–C5 alkanes. As a result of superfast heating under microwave irradiation,the conversion of hexadecane was calculated to be between 40 and 60%because some hexadecane reactant was rapidly volatilized at the startof the reactions,17 and the H2 yield obtainedfrom the process was about 60%.17In Within different particle sizes,60–80 nm Fe particles mosteffectively catalyzed the dehydrogenation of hexadecane under microwaveirradiation, whereas importantly no measurable catalytic reactionwas observed on 841 μm Fe particles. For chemical catalysisto occur, catalyst particles must reach the necessary temperatureto initiate the reactions, but 841 μm Fe particles were heatedpoorly under microwave due to their large particle size see 3.1.2 selectivityof two mixture samples of Fe (60–80 nm) + AC and Fe (841 μm)+ AC were about 85 and 75 vol %, respectively, whereas only 72 and57 vol % H2 selectivity was obtained on pure 60–80nm Fe and AC particles ,and solid carbon. For AC, 57 vol % H2, 24 vol % CH4, 10 vol % C2H4, and 5 vol % C3–C5 were detected in the produced gases (2 selectivity. We believe the structure of Fe/AC (20) was whatcaused the limited improvement in H2 selectivity when Fewas added. In the prepared Fe/AC catalyst .16 The Fe–Ni alloycatalyst has a smaller particle size than that of Fe and Ni nanoparticles,which also show an extremely high hydrogen selectivity. We found thatthe presence of nickel in an iron-based catalyst improves the dispersionof metal particles on the SiC surface and suppresses the formationof COx.16In contrast, the use of SiC as a supporting material significantlyimproves the catalytic performance for hydrogen production. In fact,some 93–98 vol % Harticles 8b. In th16 Moreover, the smooth surfaceof SiC should enhance the molecular diffusion and improve the transportof both incoming reactants and departing products,5 especially when there is a possible temperature gradientbuilt between the Fe metal particles and the SiC support. Fe nanoparticles,on the other hand, are dominant in the catalytic scission of chemicalC–H bonds in the hydrocarbons.In the SiC-supported iron-based metal catalyst system, both SiCand small iron nanoparticles are excellent microwave absorbers. Inaddition, Fe nanoparticles are uniformly dispersed on the SiC surfaceand are exposed to the incoming reactant hydrocarbon molecules. Importantly,this combines the advantages of both materials that respond to microwaves.The constituent SiC is mechanically very strong and has an exceptionallyhigh thermal conductivity. These intrinsic properties of SiC clearlycontribute to the development of a thermal balance in the reactionsystem.17 on the effectof Fe loading on SiC, we concluded that the Fe loading at the lowerlevels, less than 10 wt %, is preferable for higher levels of hydrogenproduction in the evolved gases. Further investigation of the Fe particlesize used in the Fe/SiC catalysts revealed that the catalytic performanceis size dependent  at the operating frequency. The combination of physicallymixed Fe metal particles and AC has synergistic effects in improvingthe heating ability and subsequently enhances the overall catalyticactivity of the mixture. The suitable metal and support combinationof SiC-supported Fe and Ni catalysts gave exceptional yields of hydrogenproduction under microwave initiation. These combinations form aneffective microwave-harvesting catalyst system for microwave-initiateddeep dehydrogenation reactions. From this study, we hope to have begunthe process of identifying the fundamental mechanism of interactionbetween microwave radiation and an active catalyst, which is criticalfor the complete catalytic process. Perhaps the most important findingfrom our study is the size-induced transition of particulate catalyticmetals from a microwave “reflector” to “absorber”and that electronic transition must be carefully considered in theselection of efficient metal catalysts. Thus, the physical size ofsmall conducting metal catalyst particles will decisively affect theirheating characteristics and hence their catalytic performance undermicrowave initiation.In this work, we have demonstratedthat the optimal particle sizeof Fe metal catalysts for the microwave-initiated deep dehydrogenation,or hydrogen-stripping from a model hydrocarbon, hexadecane, is between80 and 120 nm. The process is clearly highly dependent on the ratioof mean particle radius to the skin depth of iron (Since the heating mechanism of microwavesis fundamentally differentfrom conventional thermal heating, incoming microwaves will interactdirectly with each material independently. Thus, the catalyst designfor microwave-initiated catalysis should carefully consider the microstructural,electrical, and magnetic parameters, such as particle size, electricconductivity, saturation magnetization, and dielectric and catalyticproperties of all constituent materials.2—or even CO2-free—hydrogenwithin a carefully constructed catalyst system design/optimization.The guidance outlined here on catalyst design and optimization throughsize-dependent effects will hopefully be of help in other importantcatalytic chemical reactions initiated by microwaves, particularlythose in producing hydrogen from fossil fuels themselves without CO2 emission.Finally, in this applicationof microwave-initiated catalysis,we note that this work provides an excellent route for producing ultralowCO


To identify risk factors associated with short-term postoperative complications in patients with gastrointestinal cancer and develop and validate prediction models to predict the probability of complications.A total of 335 patients enrolled in the primary cohort of this study were divided into training and validation sets in a chronological order. Using univariate and multivariate logistic regression analyses, the risk factors for postoperative complications were determined, and nomogram prediction models were constructed. The performance of the nomogram was assessed with respect to the receiver operator characteristic and calibration curves.Patients with complications had a stronger postoperative stress response and a longer duration of daily fluid intake/output ratio >1 after surgery. Logistic analysis revealed that body mass index (BMI), body temperature on POD4 (T.POD4), neutrophil percentage on POD4 (N.POD4), fasting blood glucose on POD4 (FBG.POD4), and the presence of fluid intake/output ratio <1 within POD4 were risk factors for POD7 complications, and that BMI, T.POD7, N.POD7, FBG.POD4, FBG.POD7, and the duration of daily fluid intake/output ratio >1 were risk factors for POD30 complications. The areas under the curve of Nomogram-A for POD7 complications were 0.867 and 0.833 and those of Nomogram-B for POD30 complications were 0.920 and 0.918 in the primary and validation cohorts, respectively. The calibration curves showed good consistency in both cohorts.This study presented two nomogram models to predict short-term postoperative complications in patients with gastrointestinal cancer. The results could help clinicians identify patients at high risk of complications within POD7 or POD30. Gastric and colorectal cancers are among the top five causes of morbidity and mortality among all cancer patients in China , 2. SurgMost gastrointestinal surgical complications are not obvious and are difficult to detect in the early stages . TherefoThe occurrence of complications is intimately linked to the stress response after surgery, and their occurrence usually indicates a high level of stress in the body. The high stress response in the early postoperative period also indicates that postoperative complications are likely to occur, which provides a reference point for predicting postoperative complications , 10.Minimally invasive surgery combined with enhanced recovery after surgery is an important aspect of standardized gastrointestinal tumor management. Clinical trials have shown that they can improve short-term outcomes and long-term survival. However, postoperative complications remain an important clinical problem –13. The This study included patients with gastrointestinal tumors who underwent standard surgical treatment between June 2020 and July 2021 in the Gastrointestinal Unit of Yantai Yuhuangding Hospital, Qingdao University. The inclusion criteria were as follows: (i) age ≥18 years; (ii) no obvious contraindications in preoperative examination; (iii) preoperative pathology determined to be gastric or colorectal cancer; (iv) Eastern Cooperative Oncology Group performance status of ≤3; and (v) life expectancy of ≥6 months. The exclusion criteria were as follows: (i) without complete baseline examination; (ii) with the presence of secondary tumor or comorbidities on the preoperative examination that required emergency surgery; (iii) current or a history of malignancy in addition to gastrointestinal tumors; (iv) with other diseases that could either affect the study results or were uncontrollable.This retrospective study was approved by the ethics committee of Yantai Yuhuangding Hospital, Qingdao University, and the requirement for informed consent was waived due to the retrospective nature of the study.Perioperative clinical data, such as baseline characteristics and laboratory results, were collected from each patient. The baseline characteristics included sex, age, body mass index (BMI), history of smoking and alcohol consumption, neoadjuvant chemoradiotherapy , fasting blood glucose (FBG), alanine aminotransferase, and aspartate aminotransferase levels on postoperative days 1 (POD1), 4 (POD4), and 7 (POD7). We also recorded the daily fluid intake and output per patient, including perioperative infusion, bleeding, drainage, and urine volume. We further calculated the daily fluid output and fluid difference using the following formula:VOL is short for the letter “volume”. Invisible water loss was set at 900 ml and increased with increasing body temperature; by 200 ml when body temperature was between 37.3 °C and 37.7 °C, 500 ml between 37.8 °C and 38.3 °C, and 800 ml above 38.3 °C. Then, we assessed whether each patient had a fluid intake/output ratio <1 within POD4 (It means two consecutive days of daily fluid intake/output ratio <1 within POD4) and the final duration of daily fluid intake/output ratio >1. The first day of the first two consecutive days with a ratio <1 was estimated as the final duration of fluid intake/output ratio >1 from POD1. If there were two consecutive days without a ratio <1 within POD7, the duration was estimated as 7 days when there was a ratio <1 on POD7 and 8 days when there was still a ratio >1 on POD7. To explore the stress status of the patients, we measured levels of stress indicators, including perioperative C-reactive protein (CRP), interleukin-6 (IL-6), and cortisol.Note that In addition, according to each of their postoperative monitored vital signs, laboratory test results, and postoperative treatment measures, the presence of postoperative complications was assessed and recorded within POD7 or POD30 based on the first day of its appearance. Each postoperative complication was graded according to the Clavien–Dindo classification .Preoperative laboratory tests and examinations were performed in all patients to exclude clear contraindications to surgery. All surgeries were performed by five gastrointestinal specialists who performed more than 80 similar surgeries annually at Yantai Yuhuangding Hospital. At the end of the surgery, one or two drains were placed at the anastomosis and closed stump subcutaneously in all patients. All patients were routinely treated with prophylactic antibiotics, nutritional support, pain relief, and other symptomatic treatments after surgery. Postoperative routine blood tests and biochemistry were performed every 3 days. Gastrointestinal tract images was reviewed before discharge, and drains were removed if there were no signs of leakage. Simultaneously, patients were closely monitored for postoperative complications during the treatment process. Once they occurred, early intervention was provided.We identified independent risk factors associated with postoperative complications by univariate and multifactorial logistic regression analyses, and the nomogram was built based on the independent risk factors in the multivariate analysis. First, we identified the independent risk factors associated with POD7 complications by using research variables and the presence or absence of a fluid intake/output ratio <1 within POD4 and then developed Nomogram A (Nomogram-A). Secondly, we identified the independent risk factors associated with POD30 complications by using research variables and the final duration of fluid intake/output ratio >1 within POD7 and then developed Nomogram B (Nomogram-B).The recognition performance of Nomograms-A and -B were evaluated using receiver operator characteristic (ROC) curves in the training and validation sets . Compariχ2 test or Fisher's exact test in the baseline table. Correlation analysis was performed using Spearman's correlation test. The independent risk factors were determined using univariate and multifactorial logistic regression analyses. Nomograms and calibration curves were plotted using the “RMS” software package. The ROC curves were plotted using the “pROC” software package. For all tests, a two-sided P < 0.05 was considered statistically significant.Statistical analyses were performed using SPSS (version 26.0) and R (version 3.6.2) software. Exact variables were analyzed using Student's t-test, and categorical variables were analyzed using the n = 223) and validation (n = 112) sets. The patients were also divided into a group with (n = 233) and without (n = 102) complications. Baseline patient characteristics and outcomes of the training and validation sets are shown in A total of 335 patients (225 men and 110 women) were included in this study and were divided chronologically into training , respectively . Accordin = 168). Comparing the stress indicators between the groups with and without complications, the CRP, IL-6, and cortisol levels were significantly higher in the group with complications than in those without complications on POD1, POD4, and POD7 (P < 0.05); however, there was no significant difference between the groups before surgery (P > 0.05)  .The results of this study further confirm that patients with postoperative complications generally have a stronger postoperative stress response than those without postoperative complications, and the presence of a strong stress response in the early postoperative period may reflect the occurrence of postoperative complications.P > 0.05) (P < 0.05), and the fluid gap increased significantly from POD4. This gap between the two groups persisted until the last day of statistical analysis. Short-term postoperative complications tended to occur 3–5 days after surgery; therefore, we considered this increase in variance to be related to the timing of postoperative complications. We also compared the presence or absence of fluid intake/output ratio <1 within POD4 and the final duration of fluid intake/output ratio >1 between both groups. Patients with complications were less likely to have a fluid intake/output ratio <1 within POD4  and had a significantly longer duration of fluid intake/output ratio >1 postoperatively than those without complications .This study also analyzed perioperative fluid volumes between the groups of patients with and without postoperative complications. Intraoperative bleeding and infusion volumes in the group with complications were not significantly different from those in the group without complications ( > 0.05) . In contThrough our study, we considered that changes in postoperative fluid difference may be associated with the development of postoperative complications and further discuss whether they could be risk factors for the development of postoperative complications.First, we used clinical data within POD4 and identified five risk factors associated with the occurrence of complications within POD7 by univariate and multifactorial logistic regression analyses : BMI, boSimilarly, we identified six independent risk factors associated with the occurrence of complications within POD30 in AP = 0.755 vs. 0.738 .In the present study, we successfully developed and validated nomograms for predicting postoperative complications within POD7 and POD30 in patients with gastrointestinal tumors. Both nomogram models were developed based on routine clinical indicators, including body temperature, neutrophil percentage, fasting glucose, and fluid volume within POD7. The AUCs of Nomogram-A and Nomogram-B were both greater than 0.8 in the training and validation sets, which may achieve the best performance in predicting the likelihood of postoperative complications. Comprehensively, this model is used to identify people at high risk of postoperative complications, thereby reducing its impact on postoperative recovery. The goal of both models is to improve short-term outcomes and quality of life after surgery and to reduce healthcare costs.It has been documented that the occurrence of postoperative complications is closely associated with stress, and their occurrence usually indicates a strong stress response in the patient that induces hypermetabolism , 18. TheIn our study, we also found a higher level of the stress response in patients with postoperative complications. In line with the study by Espiner EA, the alteration of stress results in increased water and sodium retention and further leads to more liquid intake than output, ultimately resulting in a higher daily fluid intake/output ratio . And we Our study also validated the correlation between postoperative complications and routine monitoring indicators, such as body temperature, neutrophil percentage, and FBG . Slight Our study had some limitations. First, this study was a retrospective study that might have led to bias. Further prospective data are needed to validate the accuracy of our model. Second, a small number of patients were not included in this study owing to missing data, which resulted in a higher population of the group with complications. This may also lead to selection bias. Third, because of the high cost of measuring stress indicators, we only collected partial data from training set. And we will further consider ending the limitations by future prospective studies needed.This study presents two nomogram models for predicting short-term postoperative complications in patients with gastrointestinal tumors. Our results can help clinicians identify patients at high risk of complications within POD7 or POD30. In addition, we explored the correlation between postoperative complications and fluid intake and output under the framework of pathophysiology and stress response and successfully identified new risk factors for complications. This study also provides a novel idea for predicting postoperative complications.


To report different biometric measurements in high myopia associated with different underlying ocular and genetic conditions.Retrospective study.Patients with high myopia.We searched the Stanford Research Repository tool to identify patients with the diagnosis of high myopia who were seen by a single provider at Byers Eye Institute at Stanford from January 2019 to March 2022. We performed a chart review and included eyes that had high myopia and ocular biometric measurements at any time point after January 2019. We divided our cohort into 5 different groups: (1) isolated high myopia (IHM) (control group); (2) retinopathy of prematurity (ROP); (3) familial exudative vitreoretinopathy; (4) Marfan syndrome; and (5) Stickler syndrome.Biometric measurements.A total of 246 patients (432 eyes) were included as follows: 202 patients (359 eyes) in the IHM group, 17 patients (27 eyes) in the ROP group, 7 patients (12 eyes) in the familial exudative vitreoretinopathy group, 8 patients (14 eyes) in the Marfan group, and 12 patients (20 eyes) in the Stickler group. The ROP group showed significantly shorter axial lengths, shallower anterior chambers, and thicker lenses compared with the IHM group. The Marfan group showed significantly flatter corneas and thicker lenses compared with the IHM group. The Stickler group showed significantly longer axial lengths compared with the IHM group.High myopia is associated with variable biometric measurements according to underlying ocular or genetic conditions. Retinopathy of prematurity-associated high myopia is primarily lenticular, while Stickler syndrome-associated high myopia is axial. Marfan syndrome-associated high myopia is derived from both axial and lenticular mechanisms. We sought to investigate if etiology impacted findings.This was a retrospective, observational study in which we searched the Stanford Research Repository tool to identify patients with the diagnosis of progressive high (degenerative) myopia, using International Classification of Diseases codes H44.20, 21, 22, and 23, who were seen by a single provider (D.M.) at Byers Eye Institute at Stanford from January 2019 to March 2022. We performed a chart review and included eyes that had a confirmed diagnosis of high myopia, defined as spherical equivalent refractive error of ≤ −6.0 diopters or axial length ≥ 26.5 mm, and had ocular biometric measurements at any time point after January 2019. We excluded eyes that did not meet the criteria of high myopia, eyes with no biometric measurements, eyes with scleral buckling procedures, and eyes with a history of trauma or infection.The study was conducted in compliance with the Declaration of Helsinki, the United States Code of Federal Regulations Title 21, and the Harmonized Tripartite Guidelines for Good Clinical Practice (1996). Stanford University Institutional Review Board approved the study under protocol number 36544, and an informed consent waiver was obtained as the charts of enrolled patients were retrospectively reviewed.We collected demographic data, underlying ocular and genetic conditions, manifest refraction measurements, biometric measurements, and optical coherence tomography (OCT) findings. We divided our cohort into 5 different groups according to the presence or absence of the most common underlying ocular or genetic conditions in our cohort namely (1) IHM (control group); (2) ROP; (3) FEVR; (4) Marfan syndrome; and (5) Stickler syndrome. The IHM group included eyes with no known underlying ocular or genetic conditions.Biometric data were collected using IOL Master  including axial length (AXL), average keratometric readings (AK), anterior chamber depth (ACD), lens thickness (LT), and white to white. After controlling for age and sex, we compared different biometric measurements across the 5 different groups as well as individually between the control group and each of the other groups. Refraction, LT, and ACD were not considered in eyes with cataract greater than grade 1 nuclear sclerosis, pseudophakia, or aphakia. Refraction and AK were not considered in eyes with history of refractive surgery.Macular OCT images were graded into eyes with and without fovea plana, which was defined as the absence of a normal foveal pit on OCT. The relationship between fovea plana and axial length was explored.http://redcap.stanford.edu) is developed and operated by Stanford Medicine Research IT team. The REDCap platform services at Stanford are subsidized by (a) Stanford School of Medicine Research Office and (b) the National Center for Research Resources and the National Center for Advancing Translational Sciences, National Institutes of Health, through grant UL1 TR001085.We used the Stanford REDCap for the collection and management of data. The Stanford REDCap platform .A total of 516 patients (1032 eyes) were initially identified through the Stanford Research Repository tool. A total of 256 patients (449 eyes) met the inclusion criteria. Ten patients (17 eyes) were further excluded as they did not fit any of the 5 groups and had miscellaneous underlying ocular or genetic conditions including ocular albinism, choroideremia, X-linked retinoschisis, and homocystinuria. A total of 246 patients (432 eyes) were included in the final analysis .Figure 1P < 0.001 for all 3 parameters). Although AK and white-to-white measurements were higher and lower, respectively, in the ROP group, the differences were not statistically significant after controlling for age, sex, and refraction . However, after adjustment, the difference was not statistically significant. None of the other measurements was statistically significant in the univariate analysis . None of the other measurements was statistically different between the 2 groups . None of the other measurements was statistically different between the 2 groups .Eighteen eyes were graded with fovea plana on OCT. Most of these eyes were associated with ROP  and 1 eye was associated with Stickler syndrome. In the ROP group, the mean (standard deviation) of AXL in eyes with (n = 17) and without (n = 10) fovea plana was 24.8 ± 1.2 mm and 26.1 ± 2.6 mm, respectively, and the difference was not statistically significant , and thicker lens when compared with eyes with IHM. Similarly, eyes with high myopia associated with Marfan syndrome have flatter corneas but thicker lenses compared with eyes with IHM. Eyes with Stickler syndrome have higher refractive errors and AXLs than eyes with IHM.In our ROP group, despite the fact that refractive errors were significantly higher compared with the IHM, AXL measurements were significantly shorter. In addition, LT in our ROP group was significantly higher than in the IHM group. This supports the conclusion that high myopia in association with ROP is refractive rather than axial. Furthermore, after controlling for refraction, LT remained significantly higher than IHM, but the AK readings were not. This supports that myopia in ROP is mainly lens induced. This is further supported by the significantly shallow AC measurements in ROP eyes compared with IHM and all other groups, which could be explained by disproportionately large lenses in shorter eyes.Our results are similar to multiple other studies which noted that in ROP, AXL and ACD measurements are shorter and lenses are thicker than in normal eyes.Choi et alKent et alOur FEVR group showed significantly shorter AXL measurements when compared with IHM before controlling for age. Following control for age and sex, the correlation became statistically insignificant. We would be careful to draw hard conclusions regarding our FEVR group given the relatively low number of eyes and patients. Qi et alIn our Marfan group, AK readings were significantly lower than all of the other groups, including IHM. Our findings are supported by multiple previous studies which showed that Marfan syndrome is associated with flat corneas.Our Marfan group also had increased LT when compared with IHM. Gehle et alOur Stickler group showed a statistically significant increase in AXL compared with IHM. Moreover, AXL measurements and refractive errors of the Stickler group were the highest in our cohort. To the best of our knowledge, this is the first time to report that Stickler syndrome is associated with higher AXL measurements when compared with high myopia due to different underlying conditions.Foveal hypoplasia, or fovea plana as described by Marmor et al,We recognize that our study has several limitations. Initial patient selection was based on International Classification of Diseases coding. We performed a meticulous chart review to account for this error. Given that all of our cohort was seen by a single retina specialist in a single tertiary center, there is a risk for selection and referral biases. The relatively small number of patients in some of our groups, namely FEVR and Marfan, could have led to missed findings and may limit the generalizability of our conclusions.High myopia is associated with variable biometric measurements according to different underlying ocular or genetic conditions. Retinopathy of prematurity-associated high myopia is primarily lenticular, while Stickler syndrome–associated high myopia is axial. Marfan syndrome–associated high myopia is derived from both axial and lenticular mechanisms.