Two-row, three-row or powered circular stapler, which to choose when performing colorectal anastomosis? A systematic review and meta-analysis.

PURPOSE: Three types of circular staplers can be used to perform a colorectal anastomosis: two-row (MCS), three-row (TRCS) and powered (PCS) devices. The objective of this meta-analysis has been to provide the existing evidence on which of these circular staplers would have a lower risk of presenting a leak (AL) and/or anastomotic bleeding (AB). METHODS: An in-depth search was carried out in the electronic bibliographic databases Embase, PubMed and SCOPUS. Observational studies were included, since randomized clinical trials comparing circular staplers were not found. RESULTS: In the case of AL, seven studies met the inclusion criteria in the PCS group and four in the TRCS group. In the case of AB, only four studies could be included in the analysis in the PCS group. The AL OR reported for PCS was 0.402 (95%-confidence interval (95%-CI): 0.266-0.608) and for AB: 0.2 (95% CI: 0.08-0.52). The OR obtained for AL in TRCS was 0.446 (95%-CI: 0.217 to 0.916). Risk difference for AL in PCS was - 0.06 (95% CI: - 0.07 to - 0.04) and in TRCS was - 0.04 (95%-CI: - 0.08 to - 0.01). Subgroup analysis did not report significant differences between groups. On the other hand, the AB OR obtained for PCS was 0.2 (95% CI: 0.08-0.52). In this case, no significant differences were observed in subgroup analysis. CONCLUSION: PCS presented a significantly lower risk of leakage and anastomotic bleeding while TRCS only demonstrated a risk reduction in AL. Risk difference of AL was superior in the PCS than in TRCS.

Incidence of anastomotic leakage using powered circular staplers versus manual circular staplers for left colorectal anastomosis: a cost-effectiveness analysis.

BACKGROUND: Colorectal anastomotic leakage causes severe consequences for patients and healthcare system as it will lead to increased consumption of hospital resources and costs. Technological improvements in anastomotic devices could reduce the incidence of leakage and its economic impact. The aim of the present study was to assess if the use of a new powered circular stapler is cost-effective. METHOD: This observational study included patients undergoing left-sided circular stapled colorectal anastomosis between January 2018 and December 2021. Propensity score matching was carried out to create two comparable groups depending on whether the anastomosis was performed using a manual or powered circular device. The rate of anastomotic leakage, its severity, the consumption of hospital resources, and its cost were the main outcome measures. A cost-effectiveness analysis comparing the powered circular stapler versus manual circular staplers was performed. RESULTS: A total of 330 patients were included in the study, 165 in each group. Anastomotic leakage rates were significantly different (p = 0.012): 22 patients (13.3%) in the manual group versus 8 patients (4.8%) in the powered group. The effectiveness of the powered stapler and manual stapler was 98.27% and 93.69%, respectively. The average cost per patient in the powered group was €6238.38, compared with €9700.12 in the manual group. The incremental cost-effectiveness ratio was - €74,915.28 per patient without anastomotic complications. CONCLUSION: The incremental cost of powered circular stapler compared with manual devices was offset by the savings from lowered incidence and cost of management of anastomotic leaks.

Three-dimensional endoanal ultrasound to assess the validity of Goodsall's Rule and the Midline Rule in predicting the path of perianal fistula-in-ano and the location of the internal opening.

BACKGROUND: Correct identification of the internal opening is essential in the management of perianal fistulae. The aim of this study was to assess the validity of Goodsall's Law and the Midline Rule in predicting the path of perianal fistula-in-ano and the location of the internal opening using 3-dimensional endoanal ultrasound. METHODS: An observational study including patients diagnosed with fistula-in-ano, at our institution from January 2006 to December 2020 was performed. Location and distance from the anal verge of the external opening, internal opening, and the path of the fistulous tract were recorded during physical examination and endoanal ultrasound. Goodsall's and Midline rules were applied to all fistulae according to the location of the external opening. The location of the internal opening as predicted by either rule was then compared to the real location of the internal opening identified during endoanal ultrasound examination. RESULTS: Nine hundred and nine patients [657 (72.3%) males, mean age 50.78 (49.84-51.72) years] were included. 665 (73.2%) of fistulae were transsphinteric. Concordance between predicted internal opening site and the true internal opening location was 0.601 (good match) for Goodsall's rule, and 0.416 (moderate match) for the Midline rule. Goodsall's rule proved to be more predictive in the anterior plane (p < 0.001). Both rules were more likely to make a correct diagnosis in posterior fistulae located 4.5-7.5 mm from the anal verge. CONCLUSIONS: Both Midline and Goodsall's rules are highly predictive of the course of fistula tracts located in the posterior plane, and are lower for anterior located fistulae, female patients and when the external opening is located further from the anal verge.

Does delaying curative surgery for colorectal cancer influence long-term disease-free survival? A cohort study.

BACKGROUND: Surgical wait list time is a major problem in many health-care systems and its influence on survival is unclear. The aim of this study is to assess the impact of wait list time on long-term disease-free survival in patients scheduled for colorectal cancer resection. MATERIALS AND METHODS: A prospective study was carried out in patients with colorectal cancer scheduled for surgery at a tertiary care center. Wait list time was defined as the time from completion of diagnostic workup to definitive surgery and divided into 2-week intervals from 0 to 6 weeks. The outcome variables were 2-year and 5-year disease-free survival. RESULTS: A total of 602 patients, 364 (60.5%) male, median age 73 years (range = 71) were defined. The median wait list time was 28 days (range = 99). Two and 5-year disease-free survival rates were 521 (86.5%) and 500 (83.1%) respectively. There were no differences in 2-year or 5-year disease-free survival for the whole cohort or by tumor stage between wait list time intervals except for AJCC stage II tumors which showed a higher 5-year disease-free survival for the 2-4 and 4-6-week wait list time interval (p = 0.021). CONCLUSIONS: Time from diagnosis to definitive surgery up to 6 weeks is not associated with a decrease in 2-year or 5-year disease-free survival (DFS) in AJCC stage I through III colorectal cancer patients. These are important findings in the light of the COVID-19 pandemic and offer a window of opportunity for preoperative optimization and prehabilitation.

Impact of the novel powered circular stapler on risk of anastomotic leakage in colorectal anastomosis: a propensity score-matched study.

BACKGROUND: Several risk factors for anastomotic leakage (AL) following colorectal surgery have been described. Improvement in devices for performing anastomosis is a modifiable factor that could reduce AL rates. The aim of this study was to assess the impact of technical improvements in the Echelon Circular™ powered stapler (ECPS) on the left-sided colorectal AL rate compared to current manual circular staplers (MCS). METHODS: A cohort study was carried out on consecutive patients between January 2017 and February 2020 in whom left-sided stapled colorectal anastomosis above 5 cm from anal verge was performed. The primary end point was the risk of AL depending on the type of circular stapler used. The ECPS cases were matched to MCS cases by propensity score matching to obtain comparable groups of patients. RESULTS: Two hundred seventy-nine patients met the inclusion criteria. A MCS anastomosis was performed in 218 patients and ECPS anastomosis in 61 (21.9%). Overall, AL was observed in 25 (9%) cases. Factors significantly associated with AL were American Society of Anesthesiologists score (p = 0.025) and type of circular stapler used (p = 0.021). After adjusting the cases with propensity score matching (119 cases MCS versus 60 ECPS), AL was observed in 14 (11.8%) patients in MCS group and in 1 (1.7%) patient in the ECPS group (p = 0.022). AL in the MCS group required reoperation in seven cases (5.8%), the remaining seven patients were treated conservatively. The patient in the ECSP group required an urgent Hartmann's procedure CONCLUSIONS: The ECPS device could have a positive impact by reducing AL rates in left-sided colorectal anastomosis. Multicenter controlled trials are needed for stronger evidence to change practice.

Healing criteria: How should an episode of benign paroxistic positional vertigo of posterior semicircular canal's resolution be defined? Prospective observational study.

OBJECTIVES: To compare the outcome of the Epley maneuver (EM) in benign paroxysmal positional vertigo of the posterior canal (CSP-BPPV) depending on the definition used for recovery. DESIGN: Multicenter observational prospective study. SETTING: Otoneurology Units of 5 tertiary reference hospitals. PARTICIPANTS: All patients presenting with unilateral CSP-BPPV assisted for 1-year period. EXCLUSION CRITERIA: Spontaneous nystagmus, positive McClure-Pagnini maneuver, positive bilateral Dix-Hallpike maneuver (DHM), positive DHM for vertigo but negative for nystagmus and atypical nystagmus. MAIN OUTCOME MEASURES: Response to EM was measured after 7 days in 3 different outcomes: disappearance of nystagmus during the DHM in the follow-up visit, disappearance of vertigo during the DHM and general status (GS) during daily life activities. RESULTS: 264 patients were recruited (68 male/166 female, mean age 62 years). After the EM, nystagmus disappeared in 67% of them, vertigo in 54% and 36% were asymptomatic in their daily life. These outcomes were strongly correlated, but they were not concordant in a clinically significant group of cases; only the 26% of patients met all of them. The healing process follows the next sequence: negativization of positional nystagmus, then disappearance of positional vertigo and, finally, the improvement of GS during daily life activities. CONCLUSION: Nowadays, healing criteria for the resolution of an PSC-BPPV episode have not been specifically defined yet. Provided that other otoneurological disorders have been ruled out, the next resolution criterion is proposed: absence of nystagmus and specifically during control DHM and disappearance of symptoms during daily life activities.

Subcellular Localizations of RIG-I, TRIM25, and MAVS Complexes.

The retinoic acid-inducible gene 1 (RIG-I) signaling pathway is essential for the recognition of viruses and the initiation of host interferon (IFN)-mediated antiviral responses. Once activated, RIG-I interacts with polyubiquitin chains generated by TRIM25 and binds mitochondrial antiviral signaling protein (MAVS), leading to the production of type I IFN. We now show specific interactions among these key partners in the RLR pathway through the use of bimolecular fluorescence complementation (BiFC) and super-resolution microscopy. Dimers of RIG-I, TRIM25, and MAVS localize into different compartments. Upon activation, we show that TRIM25 is redistributed into cytoplasmic dots associated with stress granules, while RIG-I associates with TRIM25/stress granules and with mitochondrial MAVS. In addition, MAVS competes with TRIM25 for RIG-I binding, and this suggests that upon TRIM25-mediated activation of RIG-I, RIG-I moves away from TRIM25 to interact with MAVS at the mitochondria. For the first time, the distribution of these three proteins was analyzed at the same time in virus-infected cells. We also investigated how specific viral proteins modify some of the protein complexes in the pathway. The protease NS3/4A from hepatitis C virus redistributes the complexes RIG-I/MAVS and MAVS/MAVS but not RIG-I/TRIM25. In contrast, the influenza A virus NS1 protein interacts with RIG-I and TRIM25 in specific areas in the cell cytoplasm and inhibits the formation of TRIM25 homocomplexes but not the formation of RIG-I/TRIM25 heterocomplexes, preventing the formation of RIG-I/MAVS complexes. Thus, we have localized spatially in the cell different complexes formed between RIG-I, TRIM25, and MAVS, in the presence or absence of two viral IFN antagonistic proteins. IMPORTANCE: The first line of defense against viral infections is the innate immune response. Viruses are recognized by pathogen recognition receptors, such as the RIG-I like receptor family, that activate a signaling cascade that induces IFN production. In the present study, we visualized, for the first time in cells, both in overexpression and endogenous levels, complexes formed among key proteins involved in this innate immune signaling pathway. Through different techniques we were able to analyze how these proteins are distributed and reorganized spatially within the cell in order to transmit the signal, leading to an efficient antiviral state. In addition, this work presents a new means by how, when, and where viral proteins can target these pathways and act against the host immune system in order to counteract the activation of the immune response.

Lithium effects on the mechanical and electronic properties of germanium nanowires.

Semiconductor nanowire arrays promise rapid development of a new generation of lithium (Li) batteries because they can store more Li atoms than conventional crystals due to their large surface areas. During the charge-discharge process, the electrodes experience internal stresses that fatigue the material and limit the useful life of the battery. The theoretical study of electronic and mechanical properties of lithiated nanowire arrays allows the designing of electrode materials that could improve battery performance. In this work, we present a density functional theory study of the electronic band structure, formation energy, binding energy, and Young's modulus (Y) of hydrogen passivated germanium nanowires (H-GeNWs) grown along the [111] and [001] crystallographic directions with surface and interstitial Li atoms. The results show that the germanium nanowires (GeNWs) with surface Li atoms maintain their semiconducting behavior but their energy gap size decreases when the Li concentration grows. In contrast, the GeNWs can have semiconductor or metallic behavior depending on the concentration of the interstitial Li atoms. On the other hand, Y is an indicator of the structural changes that GeNWs suffer due to the concentration of Li atoms. For surface Li atoms, Y stays almost constant, whereas for interstitial Li atoms, the Y values indicate important structural changes in the GeNWs.

Propensity score analysis of postoperative and oncological outcomes after surgical treatment for splenic flexure colon cancer.

PURPOSE: The surgical treatment of splenic flexure colon cancer (SFCC) is somehow not yet well standardized. Postoperative and oncological results of the three surgical techniques most commonly used to treat SFCC: extended right colectomy (ERC), egmental left colectomy (SLC), and left colectomy (LC) were evaluated. METHODS: The study included all patients with stage I-III SFCC treated by ERC, SLC, or LC between 2005 and 2016. Postoperative and long-term outcomes after the different surgical techniques were analyzed: Propensity score matching (PSM) was performed to compare the outcomes between these surgical techniques and survival analyses were performed using the Kaplan-Meier method and log-rank tests. RESULTS: A total of 170 SFCC patients were operated; ERC was performed in 71 (41.76%), SLC in 36 (21.18%), and LC in 63 (37.06%). There were no significant differences in the short and long-term postoperative outcomes. Three comparison groups were developed so that PSM could be performed between the surgical technique cases: ERC (n = 59) vs. LC (n = 50); ERC (n = 50) vs. SLC (n = 33); and SLC (n = 32) vs. LC (n = 44). No differences in the short or long-term outcomes of these techniques were observed. CONCLUSION: The short and long-term outcomes between ERC, SLC, and LC are similar. SLC should be considered oncologically as appropiate as the other more extensive resections.

Reversal of Hartmann's procedure: a single-centre experience of 533 consecutive cases.

AIM: Hartmann's procedure (HP) is common. However, restoration of intestinal continuity is not so frequent. The aim of this study was to determine predictive factors which might influence outcomes following the reversal of HP. METHOD: All consecutive patients who underwent elective and emergency HP in a single institution between January 1999 and December 2014 were included. Data concerning patient, disease and treatment features were collected. Univariate and multivariate binary logistic regression models were used to determine prognostic factors. RESULTS: A total of 533 consecutive patients underwent HP over the 16-year period. Factors that were associated with a higher probability of reversal were age (< 69 years), American Society of Anesthesiologists (ASA) grade (I or II), indication for HP (likelihood of anastomotic leakage) and length of rectal stump reaching or exceeding the sacral promontory. A reduced probability of intestinal reconstruction was associated with anal incontinence, Stage IV cancer, postoperative transfusion or elective surgery. CONCLUSION: Age, ASA grade, the indication for HP, the length of rectal stump, anal incontinence, tumour stage, postoperative transfusion and elective surgery determine the probability of reversal.

Analysis of risk factors influencing the outcome of the Epley maneuver.

Benign paroxysmal positional vertigo (BPPV) is the most frequent type of vertigo. The treatment of canalithiasis of the posterior semicircular canal consists in performing a particle-repositioning maneuver, such as the Epley maneuver (EM). However, the EM is not effective in all cases. The objective of this study is to identify risk factors, which predict the EM failure, among the clinical variables recorded in anamnesis and patient examination. This is an observational prospective multicentric study. All patients presenting with BPPV were recruited and applied the EM and appointed for a follow-up visit 7 days later. The following variables were recorded: sex, age, arterial hypertension, diabetes, hyperlipidemia, smoking habit, alcohol consumption, migraine, osteoporosis, diseases of the inner ear, previous ipsilateral BPPV, previous traumatic brain injury, previous sudden head deceleration, time of evolution, sulpiride or betahistine treatment, experienced symptoms, outcome of the Halmagyi maneuver, laterality, cephalic hyperextension of the neck, intensity of nystagmus, intensity of vertigo, duration of nystagmus, occurrence of orthotropic nystagmus, symptoms immediately after the EM, postural restrictions, and symptoms 7 days after the EM. Significant differences in the rate of loss of nystagmus were found for six variables: hyperlipidemia, previous ipsilateral BPPV, intensity of nystagmus, duration of nystagmus, post-maneuver sweating, and subjective status. The most useful significant variables in the clinical practice to predict the success of the EM are previous BPPV and intensity of nystagmus. In the other significant variables, no physiopathological hypothesis can be formulated or differences between groups are too small.

Magnetic resonance defecography versus videodefecography in the study of obstructed defecation syndrome: Is videodefecography still the test of choice after 50 years?

BACKGROUND: The aim of the present study was to evaluate the diagnostic accuracy of magnetic resonance (MR) defecography and compare it with videodefecography in the evaluation of obstructed defecation syndrome. METHODS: This was a prospective cohort test accuracy study conducted at one major tertiary referral center on patients with a diagnosis of obstructed defecation syndrome who were referred to the colorectal surgery clinic in a consecutive series from 2009 to 2012. All patients underwent a clinical examination, videodefecography, and MR defecography in the supine position. We analyzed diagnostic accuracy for MR defecography and performed an agreement analysis using Cohen's kappa index (κ) for each diagnostic imaging examination performed with videodefecography and MR defecography. RESULTS: We included 40 patients with Rome III diagnostic criteria of obstructed defecation syndrome. The degree of agreement between the two tests was as follows: almost perfect for anismus (κ = 0.88) and rectal prolapse (κ = 0.83), substantial for enterocele (κ = 0.80) and rectocele grade III (κ = 0.65), moderate for intussusception (κ = 0.50) and rectocele grade II (κ = 0.49), and slight for rectocele grade I (κ = 0.30) and excessive perineal descent (κ = 0.22). Eighteen cystoceles and 11 colpoceles were diagnosed only by MR defecography. Most patients (54%) stated that videodefecography was the more uncomfortable test. CONCLUSIONS: MR defecography could become the imaging test of choice for evaluating obstructed defecation syndrome.

Temperature and rainfall are related to fertility rate after spring artificial insemination in small ruminants.

A total number of 1092 artificial inseminations (AIs) performed from March to May were documented over four consecutive years on 10 Payoya goat farms (36° N) and 19,392 AIs on 102 Rasa Aragonesa sheep farms (41° N) over 10 years. Mean, maximum, and minimum ambient temperatures, mean relative humidity, mean solar radiation, and total rainfall on each insemination day were recorded. Overall, fertility rates were 58 % in goats and 45 % in sheep. The fertility rates of the highest and lowest deciles of each of the meteorological variables indicated that temperature and rainfall had a significant effect on fertility in goats. Specifically, inseminations that were performed when mean (68 %), maximum (68 %), and minimum (66 %) temperatures were in the highest decile, and rainfall was in the lowest decile (59 %), had a significantly (P < 0.0001) higher proportion of does that became pregnant than did the ewes in the lowest decile (56, 54, 58, and 49 %, respectively). In sheep, the fertility rates of the highest decile of mean (62 %), maximum (62 %), and minimum (52 %) temperature, RH (52 %), THI (53 %), and rainfall (45 %) were significantly higher (P < 0.0001) than were the fertility rates among ewes in the lowest decile (46, 45, 45, 45, 46, and 43 %, respectively). In conclusion, weather was related to fertility in small ruminants after AI in spring. It remains to be determined whether scheduling the dates of insemination based on forecasted temperatures can improve the success of AI in goats and sheep.

Is Streptococcus bovis a urinary pathogen?

The Streptococcus bovis group (SBG) comprises several microorganisms associated with human infections. They have been associated with bacteremia, endocarditis, biliary tract infection, meningitis, and colorectal cancer, but their role as urinary pathogens is not well known. The objective of this investigation was to discover the incidence and clinical significance of the bacteriuria associated with this complex. A retrospective analysis of all adult patients with bacteriuria caused by SBG during the period 1995-2012 was carried out. During the study period, SBG was isolated in 153 adult patients, who had a mean age of 67 years, most of them being women (80%). Most of our patients (65%) had some underlying disease, with urologic disease being the most common (37%), followed by diabetes mellitus (27%) and neurologic disease (25%). Among the 88 patients in whom we were able to correctly assess symptoms, 45% had asymptomatic bacteriuria, 35% had lower urinary tract infection, and 20% had upper urinary tract infection. In 14 cases (9%), SBG was also isolated in blood cultures. Most of the isolates of SBG (72%) were S. gallolyticus subsp. pasteurianus. All isolates were susceptible to penicillin, 98% to nitrofurantoin, and 77% to fosfomycin. Although SBG bacteriuria is uncommon, it should not always be taken as a contaminant, mainly when S. pasteurianus is isolated, because it may cause urinary tract infections and, occasionally, sepsis, whereas when S. gallolyticus is isolated from urine, it may be a marker of underlying endocarditis and colorectal cancer.

Differences between endocarditis caused by Streptococcus bovis and Enterococcus spp. and their association with colorectal cancer.

Streptococcus bovis group and Enterococcus spp. share phenotypic characteristics and intestinal habitat. Both have been associated with endocarditis and colorectal neoplasm (CRN). We studied all cases of endocarditis diagnosed between 1988 and 2014 in our centre and caused by S. bovis (109, 48.8 % of the bacteremia) and by Enterococcus spp. (36, 3.4 % of the bacteremia). Patients were seen until death or during a long-term follow-up, in order to rule out a concomitant CRN. The 109 cases of S. bovis endocarditis (SbIE) compared with the 36 caused by enterococci showed: a higher proportion of males (91 % vs. 72 %, p=0.005), more multivalvular involvement (28 % vs. 6 %, p=0.004), embolic complications (44 vs. 22 %, p=0.02) and colorectal neoplasm (64 % vs. 25 %, p=0.001). SbIE showed fewer co-morbidities (32 vs. 58 %, p=0.005), and less frequently urinary infection source (0 vs. 25 %, p=0.001) and healthcare-related infection (2 vs. 44 %, p=0.001). A total of 123 patients were followed up for an extended period (mean: 65.9 ± 57.5 months). During the follow-up, 6 of 28 (21 %) cases with enterococcal endocarditis and 43 of 95 (45.2 %, p=0.01) cases with SbIE developed a new CRN. These neoplasiae appeared a mean of 60.4 months later (range 12-181 months). Among the 43 cases with SbIE and CRN, 12 had had a previously normal colonoscopy and 31 had had a previous CRN and developed a second neoplasm. Cases of SbIE present important differences with those caused by Enterococcus spp. Colonoscopy must be mandatory both in the initial evaluation of SbIE, as during the follow-up period.

Nanomechanical properties of kidney stones, gallstones and oral stones compared with tap water scale by depth sensing indentation.

This article focuses on a description of research performed to identify structural and mechanical properties differences between calculi in stones, such as gallstones, kidney stones, dental tartar, and saliva gland sialolite, were analyzed and compared with tap water stone, in order to set interrelations. In this study, biological hard pebble-like structures were analyzed and compared among them using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), and Atomic Force Microscopy (AFM). In addition, Nanoindentation was used to obtain values as example in kidney stones the in; stiffness S = 27,827 ± 620 N/nm elastic modulus E = 27.3 ± 4.5 GPa, hardness H = 1.5 ± 0.5 GPa. Samples with the highest amounts of calcium and magnesium oxides were; Tap water stone (39.60%), followed by dental tartar (39.40%), saliva gland sialolite (29.20%), kidney stones (27.70%), and lastly the gallstones (0.30%). Kidney stones showed in particular, whewellite and kaoulinite crystallographic phases, that confers characteristics of greater crystallization with respect to the other stones. Kidney stones positioned in the major hardness stone in human body with 1.5 GPa. In general, samples with the highest amount of calcium oxides, also showed the highest mechanical properties of H and E. Microstructural characteristics and nano-hardness of tap water stone from drinking water where similar to those of dental tartar and saliva gland sialolite, more research still required to associate health concerns and tap water scale derived from drinking water known as hardwater.

Anisotropic behavior of mechanical properties for thea- andc-domains in a (001) BaTiO3single crystal.

Barium titanate (BaTiO3) single crystal with a tetragonal phase was characterized by nanoindentation. Elastic and elastic-plastic deformation regimes were obtained. The main objective was the evaluation of the anisotropic behavior related to mechanical properties associated with the cross-section of the ferroelectrica- andc-domains (In-plane and out-of-plane) in (001) configuration domains. This behavior was evaluated along a line perpendicular to the between domains, which demonstrated that the mechanical properties of the BaTiO3single crystal depend on the distance from due to the effect of the influence of the neighbor domain. A three-dimensional (3D) finite element (FE) model was developed to simulate mechanical effects revealed by the nanoindentations test. The FE simulation demonstrated that there is no simple isotropic mechanical behavior associated with the domain type. Numerical simulations and experiments performed to study ferroelastic switching domains in BaTiO3crystals revealed the interaction of the 90°-cadomain with the indentation position.

Green Synthesis for Carbon Quantum Dots via Opuntia ficus-indica and Agave maximiliana: Surface-Enhanced Raman Scattering Sensing Applications.

In this study, we present an alternative method for synthesizing carbon quantum dots (CQDs) using a green synthesis approach via extracts from Agave maximiliana and Opuntia ficus-indica(Ofi). The extracts from both plants were used as the carbon source for the CQDs. The synthesis method employs mesoporous zeolite 4A as a refractory for the thermal treatment of the samples. Transmission electron microscopy analysis established that the size of the CQDs shows a narrow distribution centered around 2 nm with a maximum size of less than 3 nm for both cases. The CQDs exhibit absorption bands associated with π-π* transitions located around 220 nm. In both cases, photoluminescence (PL) phenomenon was detected by irradiating the samples with a UV wavelength and detecting emissions close to the blue wavelength. Additionally, both kinds of CQDs were tested as surface-enhanced Raman scattering (SERS) substrates against methylene blue (MB), indicating an enhancement associated with ring deformation and stretching modes of the v(C-C) and v(C-N) bonds located around 1400 and 1620 cm-1, respectively. Complementarily, in the framework of density functional theory, H2nC2(2m+1) structures (with n = 3-5 and m = 1-3) were used as a theoretical representation of CQDs in interaction with the MB molecule. It is used for developing the analysis of charge transfer effects between both systems and for specifying elements that generate the SERS effect associated with the chemical enhancement mechanism.