Patient-derived organoid biobank identifies epigenetic dysregulation of intestinal epithelial MHC-I as a novel mechanism in severe Crohn's Disease.

OBJECTIVE: Epigenetic mechanisms, including DNA methylation (DNAm), have been proposed to play a key role in Crohn's disease (CD) pathogenesis. However, the specific cell types and pathways affected as well as their potential impact on disease phenotype and outcome remain unknown. We set out to investigate the role of intestinal epithelial DNAm in CD pathogenesis. DESIGN: We generated 312 intestinal epithelial organoids (IEOs) from mucosal biopsies of 168 patients with CD (n=72), UC (n=23) and healthy controls (n=73). We performed genome-wide molecular profiling including DNAm, bulk as well as single-cell RNA sequencing. Organoids were subjected to gene editing and the functional consequences of DNAm changes evaluated using an organoid-lymphocyte coculture and a nucleotide-binding oligomerisation domain, leucine-rich repeat and CARD domain containing 5 (NLRC5) dextran sulphate sodium (DSS) colitis knock-out mouse model. RESULTS: We identified highly stable, CD-associated loss of DNAm at major histocompatibility complex (MHC) class 1 loci including NLRC5 and cognate gene upregulation. Single-cell RNA sequencing of primary mucosal tissue and IEOs confirmed the role of NLRC5 as transcriptional transactivator in the intestinal epithelium. Increased mucosal MHC-I and NLRC5 expression in adult and paediatric patients with CD was validated in additional cohorts and the functional role of MHC-I highlighted by demonstrating a relative protection from DSS-mediated mucosal inflammation in NLRC5-deficient mice. MHC-I DNAm in IEOs showed a significant correlation with CD disease phenotype and outcomes. Application of machine learning approaches enabled the development of a disease prognostic epigenetic molecular signature. CONCLUSIONS: Our study has identified epigenetically regulated intestinal epithelial MHC-I as a novel mechanism in CD pathogenesis.

Clinical and biological markers predictive of treatment response associated with metastatic pancreatic adenocarcinoma.

BACKGROUND: Chemotherapy for metastatic pancreatic adenocarcinoma (PDAC) offers limited benefits, but survival outcomes vary. Reliable predictive response biomarkers to guide patient management are lacking. METHODS: Patient performance status, tumour burden (determined by the presence or absence of liver metastases), plasma protein biomarkers (CA19-9, albumin, C-reactive protein and neutrophils) and circulating tumour DNA (ctDNA) were assessed in 146 patients with metastatic PDAC prior to starting either concomitant or sequential nab-paclitaxel + gemcitabine chemotherapy in the SIEGE randomised prospective clinical trial, as well as during the first 8 weeks of treatment. Correlations were made with objective response, death within 1 year and overall survival (OS). RESULTS: Initial poor patient performance status, presence of liver metastases and detectable mutKRAS ctDNA all correlated with worse OS after adjusting for the different biomarkers of interest. Objective response at 8 weeks also correlated with OS (P = 0.026). Plasma biomarkers measured during treatment and prior to the first response assessment identified ≥10% decrease in albumin at 4 weeks predicted for worse OS (HR 4.75, 95% CI 1.43-16.94, P = 0.012), while any association of longitudinal evaluation of mutKRAS ctDNA with OS was unclear (ß = 0.024, P = 0.057). CONCLUSIONS: Readily measurable patient variables can aid the prediction of outcomes from combination chemotherapy used to treat metastatic PDAC. The role of mutKRAS ctDNA as a tool to guide treatment warrants further exploration. CLINICAL TRIAL REGISTRATION: ISRCTN71070888; ClinialTrials.gov (NCT03529175).

SARS-COV-2 vaccine responses in renal patient populations.

BACKGROUND: Dialysis patients and immunosuppressed renal patients are at increased risk of COVID-19 and were excluded from vaccine trials. We conducted a prospective multicentre study to assess SARS-CoV-2 vaccine antibody responses in dialysis patients and renal transplant recipients, and patients receiving immunosuppression for autoimmune disease. METHODS: Patients were recruited from three UK centres (ethics:20/EM/0180) and compared to healthy controls (ethics:17/EE/0025). SARS-CoV-2 IgG antibodies to spike protein were measured using a multiplex Luminex assay, after first and second doses of Pfizer BioNTech BNT162b2(Pfizer) or Oxford-AstraZeneca ChAdOx1nCoV-19(AZ) vaccine. RESULTS: Six hundred ninety-two patients were included (260 dialysis, 209 transplant, 223 autoimmune disease (prior rituximab 128(57%)) and 144 healthy controls. 299(43%) patients received Pfizer vaccine and 379(55%) received AZ. Following two vaccine doses, positive responses occurred in 96% dialysis, 52% transplant, 70% autoimmune patients and 100% of healthy controls. In dialysis patients, higher antibody responses were observed with the Pfizer vaccination. Predictors of poor antibody response were triple immunosuppression (adjusted odds ratio [aOR]0.016;95%CI0.002-0.13;p < 0.001) and mycophenolate mofetil (MMF) (aOR0.2;95%CI 0.1-0.42;p < 0.001) in transplant patients; rituximab within 12 months in autoimmune patients (aOR0.29;95%CI 0.008-0.096;p < 0.001) and patients receiving immunosuppression with eGFR 15-29 ml/min (aOR0.031;95%CI 0.11-0.84;p = 0.021). Lower antibody responses were associated with a higher chance of a breakthrough infection. CONCLUSIONS: Amongst dialysis, kidney transplant and autoimmune populations SARS-CoV-2 vaccine antibody responses are reduced compared to healthy controls. A reduced response to vaccination was associated with rituximab, MMF, triple immunosuppression CKD stage 4. Vaccine responses increased after the second dose, suggesting low-responder groups should be prioritised for repeated vaccination. Greater antibody responses were observed with the mRNA Pfizer vaccine compared to adenovirus AZ vaccine in dialysis patients suggesting that Pfizer SARS-CoV-2 vaccine should be the preferred vaccine choice in this sub-group.

Biomediated synthesis, characterization, and biological applications of nickel oxide nanoparticles derived from Toona ciliata, Ficus carica and Pinus roxburghii.

Biomediated ecofriendly method for the synthesis of nickel oxide nanoparticles using plants extracts (Toona ciliata, Ficus carica and Pinus roxburghii) has been reported. The nanoparticles so obtained were characterized by various techniques such as ultraviolet-visible, powder X-ray diffraction, Fourier transform infrared spectroscopy, attenuated total reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis and fluorescence spectroscopy. Formation of nickel oxide nanoparticles was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction where the former technique ascertains the formation of bond between nickel and oxygen. The nickel oxide nanoparticles were found to be crystalline cubic face centered and show intense photoluminescence emission at 416, 414 and 413 nm, respectively. The antibacterial activity was studied against gram positive and gram negative bacterial species by agar well diffusion method. The nickel oxide nanoparticles show better activity against some bacterial strains with reference to the standard drugs Ciprofloxacin and Gentamicin. The anthelmintic activity against Pheretima posthuma of nanomaterials obtained from Pinus roxburghii was found to be greater than that derived from Toona ciliata and Ficus carica using the standard drug Albendazole. This method takes the advantage of the sustainable and economic approach for the synthesis of metal oxide nanoparticles.

Malus pumila and Juglen regia plant species mediated zinc oxide nanoparticles: Synthesis, spectral characterization, antioxidant and antibacterial studies.

Zinc oxide nanoparticles derived from Malus pumila (apple) and Juglen regia (walnut) plant is an attractive area of research because of their widespread use. The use of plant material to synthesize zinc oxide nanoparticles has been considered as one of the best environmentally friendly approach. This method appears to be low-cost as compare to other conventional method of synthesis. The biosynthesized nanoparticles were characterized by Ultraviolet-visible spectroscopy (UV-visible), Fourier transform infrared spectroscopy (FT-IR), Attenuated total reflectance spectroscopy (ATR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Transmission electron Microscopy (TEM) and Dynamic light scattering (DLS). The antioxidant potential has been evaluated by 2, 2-diphenyl-1-picrylhydrazyl free radical (DPPH) assay using L-ascorbic acid as a standard. The antibacterial activity was measured by agar well diffusion method to measure the efficacy of plant species extract and extract mediated zinc oxide nanoparticles against 5 g positive bacteria namely Staphylococcus aureus (S. aureus), Streptococcus mutans (S. mutans), Streptococcus pyrogenes (S. pyrogenes), Corynebacterium diphtheriae (C. diphtheriae) and Corynebacterium xerosis (C. xerosis) and 3 g negative bacteria such as Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae) and Pseudomonas aeruginosa (P. aeruginosa) bacteria with standard antibiotic for gram positive (Ciprofloxacin) and gram negative bacteria (Gentamicin).

Prevalence of depression among adults with sickle cell disease in the southern region of Saudi Arabia.

OBJECTIVES: Sickle Cell Disease (SCD) as other chronic medical conditions is commonly complicated by psychiatric symptoms. Saudi SCD patients are usually originally from Eastern and Southwestern Provinces. The main objective of our study was to evaluate the prevalence of depression among adults with SCD in southern region of Saudi Arabia. We also studied the sociodemographic profiles for these individuals. METHODS: We conducted a cross-sectional study among subjects (n=78) in Armed Forces Hospital, Southern Saudi Arabia using an Arabic version of a Hamilton Rating Scale for Depression HAM-D that has received widespread use and have undergone reliability and validity testing. The data were analyzed by SPSS 22 package program. Pearson's chi-squared test is used to examine the association between the categorical outcome variables A p-value less than 0.05 was considered statistically significant. RESULTS: Most of the participants were young adults (26.4± 9.2 years), single females not working who are originally from Jizan and Mahayel Aseer, Southern Saudi Arabia. The prevalence of depressive symptoms was 85.9%. When the association between depression in SCD patients and different demographic characters was tested, no significant relation between depression and any factors was discovered. CONCLUSION: This study confirms that depression is common in adult patients with SCD as confirmed by previous studies. On the other hand, socio-demographic factors were not significant predictors of depression in SCD patients. Further research is needed to explore the magnitude and impact of this problem at the national level.

Review of development survey of phase change material models in building applications.

The application of phase change materials (PCMs) in green buildings has been increasing rapidly. PCM applications in green buildings include several development models. This paper briefly surveys the recent research and development activities of PCM technology in building applications. Firstly, a basic description of phase change and their principles is provided; the classification and applications of PCMs are also included. Secondly, PCM models in buildings are reviewed and discussed according to the wall, roof, floor, and cooling systems. Finally, conclusions are presented based on the collected data.

A systematic literature review for evaluation of knowledge, attitude, and self-care practice regarding common eye diseases in the healthy general population.

Background and purpose: Increasing people's knowledge and then changing their attitude and practice with the aim of taking care of their eye health are very important. Considering the importance of the mentioned topic, the main goal of this study was to evaluate the knowledge, attitude, and practice about eye diseases in the general population of the world in the form of a systematic literature review. Materials and Methods: This study was a systematic literature review study, and to do it, a systematic search was conducted in internationally available databases including Web of Science, ScienceDirect, Scopus, PubMed, and Google Scholar in the time range of 1998 to 2023. Finally, considering the inclusion and exclusion criteria of the study, the results of 18 articles were extracted. Results: The findings showed that in general, people's level of knowledge about glaucoma was lower compared to other eye diseases, and the level of knowledge of men and women about eye diseases was different. In addition, the results showed that there was significant relationship between age and knowledge of various eye diseases. The results of all evaluated studies showed that people with higher education have more knowledge about eye diseases. Conclusion: Based on this, it can be concluded that as glaucoma is one of the most important causes of blindness worldwide, it is necessary to plan to increase the level of public knowledge to recognize the symptoms and complications of this disease. In addition to that, it is necessary to increase people's advertisement by ophthalmology centers and eye specialists about the use of glasses and also to encourage people to visit the eye physician regularly.

LEOPARD Syndrome with a Sporadic PTPN11 Mutation in a Saudi Patient.

LEOPARD syndrome (LS) is a rare autosomal dominant inherited or sporadic genetic disorder caused commonly by missense mutations in the protein-tyrosine phosphatase-nonreceptor type 11 (PTPN11) gene. Due to its rarity and a high chance of misdiagnosis, the epidemiological profile of LS is poorly established. To the best of our knowledge, this is the second report with a documented PTPN11 gene mutation in Saudi Arabia.

The risk of cardiovascular diseases after miscarriage, stillbirth, and induced abortion: a systematic review and meta-analysis.

Aims: Miscarriage and stillbirth have been included in cardiovascular disease (CVD) risk guidelines, however heterogeneity in exposures and outcomes and the absence of reviews assessing induced abortion, prevented comprehensive assessment. We aimed to perform a systematic review and meta-analysis of the risk of cardiovascular diseases for women with prior pregnancy loss (miscarriage, stillbirth, and induced abortion). Methods and results: Observational studies reporting risk of CVD, coronary heart disease (CHD), and stroke in women with pregnancy loss were selected after searching MEDLINE, Scopus, CINAHL, Web of Knowledge, and Cochrane Library (to January 2020). Data were extracted, and study quality were assessed using the Newcastle-Ottawa Scale. Pooled relative risk (RR) and 95% confidence intervals (CIs) were calculated using inverse variance weighted random-effects meta-analysis.Twenty-two studies involving 4 337 683 women were identified. Seven studies were good quality, seven were fair and eight were poor. Recurrent miscarriage was associated with a higher CHD risk (RR = 1.37, 95% CI: 1.12-1.66). One or more stillbirths was associated with a higher CVD (RR = 1.41, 95% CI: 1.09-1.82), CHD (RR = 1.51, 95% CI: 1.04-1.29), and stroke risk (RR = 1.33, 95% CI: 1.03-1.71). Recurrent stillbirth was associated with a higher CHD risk (RR = 1.28, 95% CI: 1.18-1.39). One or more abortions was associated with a higher CVD (RR = 1.04, 95% CI: 1.02-1.07), as was recurrent abortion (RR = 1.09, 95% CI: 1.05-1.13). Conclusion: Women with previous pregnancy loss are at a higher CVD, CHD, and stroke risk. Early identification and risk factor management is recommended. Further research is needed to understand CVD risk after abortion.

The Effect of Iron Supplementation on FGF23 in Chronic Kidney Disease Patients: a Systematic Review and Time-Response Meta-Analysis.

Fibroblast growth factor 23 (FGF23) gene is found to be responsible for autosomal dominant hypophosphatemic rickets, and is highly expressed in chronic kidney disease (CKD) and end-stage renal disease patients with iron deficiency anemia (IDA). We evaluated the efficacy of different iron treatments on FGF23 levels in dialysis-dependent and non-dialysis-dependent CKD patients with IDA. We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing different types of iron treatment versus placebo in CKD patients up to May 2020. We investigated the efficacy of iron treatment on the levels of FGF23 and C-terminal FGF23 (cFGF23) in CKD patients. We estimated weighted mean differences (WMDs) and 95% confidence intervals (CIs) using the random-effects model. Nine studies with 11 arms were included in the meta-analysis. Overall, iron treatment showed a significant reduction in FGF23 levels compared to control group (WMD: - 60.56 pg/ml, 95% CI: - 92.17, - 28.95). Compared to placebo, subgroup analysis showed that oral iron therapy (WMD: - 6.98 pg/ml, 95% CI: - 10.66, - 3.31) was more effective than intravenous (IV) iron therapy (WMD: 4.90 pg/ml, 95% CI: - 12.03, 21.83) on FGF23 levels. There was no significant change in cFGF23 levels between iron treatment and control group (WMD: - 64.72 Ru/ml, 95% CI: - 147.69, 18.25). Subgroup analysis showed that oral iron therapy resulted in a significant reduction in cFGF23 levels compared to control group (WMD: - 150.48 RU/ml, 95% CI: - 151.31, - 149.65). In conclusion, iron treatment was associated with a significant decrease in FGF23 levels in CKD patients.

The risk of cardiovascular disease in women after miscarriage, stillbirth, and therapeutic abortion: a protocol for a systematic review and meta-analysis.

BACKGROUND: Cardiovascular disease (CVD) is the leading cause of death in women, responsible for approximately a third of all female deaths. Pregnancy complications are known to be associated with a greater risk of incident CVD in mothers. However, the relationships between pregnancy loss due to miscarriage, stillbirth, or therapeutic abortion, and future maternal cardiovascular health are under-researched. This study seeks to provide an up-to-date systematic review and meta-analysis of the relationship between these three forms of pregnancy loss and the subsequent development of CVD. METHODS: This systematic review will follow the Preferred Reporting Items for Systematic Review and Meta-Analysis checklist (PRISMA) and the Meta-analyses Of Observational Studies in Epidemiology (MOOSE) Checklist. A systematic search will be undertaken using publications identified in MEDLINE (PubMed), Scopus, Web of Knowledge, the CINAHL Nursing Database, and the Cochrane Library. The eligibility of each publication will be determined by predefined selection criteria. The quality of the included studies will be rated using the Newcastle-Ottawa Scale. Pooled measures of association will be computed using random-effects model meta-analyses. Between-study heterogeneity will be assessed using the I2 statistic and the Cochrane χ2 statistic. Small study effects will be evaluated for meta-analyses with sufficient studies through the use of funnel plots and Egger's test. DISCUSSION: The results of this systematic review will discuss the long-term risks of multiple types of cardiovascular disease in women who have experienced miscarriage, stillbirth, and/or therapeutic abortion. It will contribute to the growing field of cardio-obstetrics as the first to consider the full breadth of literature regarding the association between all forms of pregnancy loss and future maternal cardiovascular disease. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration number [CRD42020167587].

Biogenic synthesis of iron oxide nanoparticles using Agrewia optiva and Prunus persica phyto species: Characterization, antibacterial and antioxidant activity.

A phytoextract mediated synthesis of iron oxide nanoparticles using Agrewia optiva (Dhaman or Biul) and Prunus persica (Peach) leaf extract as capping and stabilizing agent without using hazardous toxic chemicals via biogenic route has been studied. The biogenic method of synthesis is convenient, rapid, cost effective and ecofriendly. The green synthesized nanoparticles were characterized by Ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, Attenuated total reflectance spectroscopy, X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and dynamic light scattering measurements. The antibacterial study was determined by agar well diffusion method to measure the efficiency of both phyto species extract and its mediated iron oxide nanoparticles against five gram positive bacterial stains such as Staphylococcus aureus (S. aureus), Streptococcus mutans (S. mutans), Streptococcus pyrogenes (S. pyrogenes), Corynebacterium diphtheriae (C. diphtheriae) and Corynebacterium xerosis (C. xerosis) and three gram negative bacterial stains such as Escherichia coli (E. coli), Klebsiella pneuomoniae (K. pneuomoniae) and Pseudomonas aeruginosa (P. aeruginosa). The antibiotic Ciprofloxacin and Gentamicin have been used as reference standard drugs for gram positive and gram negative bacterial stains, respectively. The antioxidant activity of the phyto extracts and prepared nanoparticles have been performed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay employing l-ascorbic acid as a standard.

Sodium louroyl sarcosinate (sarkosyl) modulate amyloid fibril formation in hen egg white lysozyme (HEWL) at alkaline pH: a molecular insight study.

Amyloid fibril formation is responsible for several neurodegenerative diseases and are formed when native proteins misfold and stick together with different interactive forces. In the present study, we have determined the mode of interaction of the anionic surfactant sarkosyl with hen egg white lysozyme (HEWL) [EC No. 3.2.1.17] at two pHs (9.0 and 13.0) and investigated its impact on fibrillogenesis. Our data suggested that sarkosyl is promoting amyloid fibril formation in HEWL at the concentration range between 0.9 and 3.0 mM and no amyloid fibril formation was observed in the concentration range of 3.0-20.0 mM at pH 9.0. The results were confirmed by several biophysical and computational techniques, such as turbidity measurement, dynamic light scattering, Raleigh scattering, ThT fluorescence, intrinsic fluorescence, far-UV CD and atomic force microscopy. Sarkosyl was unable to induce aggregation in HEWL at pH 13.0 as confirmed by turbidity and RLS measurements. HEWL forms larger amyloid fibrils in the presence of 1.6 mM of sarkosyl. The spectroscopic, microscopic and molecular docking data suggest that the negatively charged carboxylate group and 12-carbon hydrophobic tail of sarkosyl stimulate amyloid fibril formation in HEWL via electrostatic and hydrophobic interaction. This study leads to new insight into the process of suppression of fibrillogenesis in HEWL which can be prevented by designing ligands that can retard the electrostatic and hydrophobic interaction between sarkosyl and HEWL.

Detection and sequencing of rotavirus among sudanese children.

INTRODUCTION: Diarrheal diseases are a big public health problem worldwide, particularly among developing countries. The current study was conducted to detect and characterize group A rotavirus among admitted children with gastroenteritis to the pediatric hospitals, Sudan. METHODS: A total of 755 stool samples were collected from Sudanese children with less than 5 years of age presenting with acute gastroenteritis during the period from April to September 2010. Enzyme-linked immunosorbent assay (ELISA) was used to Detection of Rotavirus antigens. Ribonucleic acid (RNAs) were extracted from rotavirus-positive stool samples using (QIAamp® Viral RNA Mini Kit). (Omniscript® Reverse Transcription kit) was used to convert RNA to complementary Deoxyribonucleic acid (cDNA). The cDNAs were used as template for detection of VP4-P (P for Protease-sensitive) and VP7-G (G for Glycoprotein) genotyping of Rotavirus using nested PCR and sequencing. RESULTS: Out of the 755 stool samples from children with acute gastroenteritis, 121 were positive for rotavirus A. Among 24 samples that were sequenced; the VP7 predominant G type was G1 (83.3%), followed by G9 (16.7%). Out of these samples, only one VP4 P[8] genotype was detected. CONCLUSION: As a conclusion the VP7 predominant G type was G1, followed by G9 whereas only one VP4 genotype was detected and showed similarity to P[8] GenBank strain. It appears that the recently approved rotavirus vaccines in Sudan are well matched to the rotavirus genotypes identified in this study, though more studies are needed.

PUBLIC HEALTH AND EPIDEMIOLOGICAL DATABASES FOR THE ENHANCEMENT OF MEDICAL EDUCATION.

The collaboration of public health education and information technology has made patient care safer and more reliable than before. Nurses and doctors use handheld computers to record a patient's medical history and check that they are administering the correct treatment. Fortunately Public Health Informatics (PHI) is the intersecting point of technology and public health. Therefore, the inclusion of online medical and epidemiology databases in the course curriculum of budding medical professionals and postgraduate students would be beneficial in enhancing the quality of health care, extensive epidemiological research, health education, health policies, health planning and consumer satisfaction as well. The purpose of this article is to discuss and provide introduction of various databases which have huge information and it could be used to enhance the public health education.

Thermo-kinetics of Forest Waste Using Model-Free Methods / Termocinética de residuos de bosque usando los métodos de modelo libre / Termocinética de resíduos de bosque usando métodos de modelo livre

Abstract Thermal behaviour of pine needles (Pinus Roxburghii) is examined through a thermogravimetry technique. The dried samples of pine needles undergo the non-isothermal decomposition at temperature range of 308-1173 K. The heating rates used for experimental purposes are: 5 ◦ C min-1, 10 ◦ C min-1 and 15 ◦ C min-1. Kinetic parameters of thermal decomposition reactions of pine needles are obtained through the model-free schemes. The estimated values of activation energy and frequency factor derived from Kissinger method are 132.77 kJ mol-1 and 13.15 x 107 min-1, respectively. Furthermore, the averaged values of the same kinetics parameters retrieved from the isoconversional methods are 82.38 kJ mol-1 and 74.833 kJ mol-1, 25.42 x 1013 min-1 and 13.449 x 1010 min-1, respectively. Instead of the Flynn-Wall- Ozawa (FWO) and Kissinger- Akahira- Sunrose (KAS) schemes, the kinetic parameters derived from the Kissinger method are relatively promising for the thermal decomposition process, since the kinetic parameters are highly affected by intermediate stages and overlapping of the concurrent reaction occurred during pyrolysis.

Resumen Se examina el comportamiento térmico de las agujas de pino (Pinus roxburghii) a través de la técnica de termogravimetría. Las muestras secas de las agujas de pino se someten a una descomposición no isotérmica en un rango de temperatura de 308-1173 K. Las tasas de calentamiento usadas para los propósitos experimentales son: 5 °C min-1, 10 °C min-1 y 15 °C min-1. Los parámetros cinéticos de las reacciones de descomposición térmica de las agujas de pino se obtuvieron a través de esquemas de modelo libre. Los valores estimados de la energía de activación y el factor de frecuencia derivado del método Kissinger son: 132.77 kJ mol-1 y 13.15 x 107 min-1, respectivamente. Por otra parte, los valores promediados de los mismos parámetros cinéticos recuperados por los métodos isoconversionales son 82.38 kJ mol-1 y 74.833 kJ mol-1, 25.42 x 1013 min-1 y 13.449 x 1010 min-1, respectivamente. A diferencia de los esquemas Flynn-Wall-Ozawa (FWO) y Kissinger-Akahira-Sunrose (KAS), los parámetros cinéticos derivados del método Kissinger son relativamente promisorios para los procesos de descomposición térmica, ya que estos parámetros se afectan grandemente por los estados intermedios y la superposición de la reacción concurrente que ocurre durante la pirólisis.

Resumo O comportamento térmico de agulhas de pinheiro (Pinus roxburghii) foi examinado por meio da técnica de gravimetria. As amostras secas das agulhas de pinheiro se submeteram a uma decomposição não-isotérmica em uma faixa de temperatura de 308-1173 K. As taxas de aquecimento usadas para propósitos experimentais foram: 5 °C min-1, 10 °C min-1 e 15 °C min-1. Os parâmetros cinéticos das reações de decomposição térmica das agulhas de pinheiro se obtiveram por meio de esquemas de modelo livre. Os valores estimados da energia de ativação e o fator de frequência derivado do método Kissinger são: 132.77 kJ mol-1 e 13.15 x 107 min-1, respectivamente. Adicionalmente, os valores médios dos mesmos parâmetros cinéticos recuperados pelos métodos isoconversionais são 82.38 kJ mol-1 e 74.833 kJ mol-1, 25.42 x 1013 min-1 y 13.449 x 1010 min-1, respectivamente. Diferentemente dos esquemas Flynn-Wall-Ozawa (FWO) e Kissinger-Akahira-Sunrose (KAS), os parâmetros cine'ticos derivados do método Kissinger são relativamente promissórios para os processos de decomposição térmica, já que estes parâmetros são altamente afetados pelos estados intermediários e sobreposição da reação concorrente que ocorre durante a pirólise.