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1.
Psychol Med ; 53(12): 5428-5441, 2023 09.
Artículo en Inglés | MEDLINE | ID: mdl-35879886

RESUMEN

BACKGROUND: The impact of the coronavirus disease 2019 (COVID-19) pandemic on mental health is still being unravelled. It is important to identify which individuals are at greatest risk of worsening symptoms. This study aimed to examine changes in depression, anxiety and post-traumatic stress disorder (PTSD) symptoms using prospective and retrospective symptom change assessments, and to find and examine the effect of key risk factors. METHOD: Online questionnaires were administered to 34 465 individuals (aged 16 years or above) in April/May 2020 in the UK, recruited from existing cohorts or via social media. Around one-third (n = 12 718) of included participants had prior diagnoses of depression or anxiety and had completed pre-pandemic mental health assessments (between September 2018 and February 2020), allowing prospective investigation of symptom change. RESULTS: Prospective symptom analyses showed small decreases in depression (PHQ-9: -0.43 points) and anxiety [generalised anxiety disorder scale - 7 items (GAD)-7: -0.33 points] and increases in PTSD (PCL-6: 0.22 points). Conversely, retrospective symptom analyses demonstrated significant large increases (PHQ-9: 2.40; GAD-7 = 1.97), with 55% reported worsening mental health since the beginning of the pandemic on a global change rating. Across both prospective and retrospective measures of symptom change, worsening depression, anxiety and PTSD symptoms were associated with prior mental health diagnoses, female gender, young age and unemployed/student status. CONCLUSIONS: We highlight the effect of prior mental health diagnoses on worsening mental health during the pandemic and confirm previously reported sociodemographic risk factors. Discrepancies between prospective and retrospective measures of changes in mental health may be related to recall bias-related underestimation of prior symptom severity.


Asunto(s)
COVID-19 , Trastornos por Estrés Postraumático , Femenino , Humanos , Trastornos por Estrés Postraumático/epidemiología , Trastornos por Estrés Postraumático/psicología , COVID-19/epidemiología , Pandemias , Depresión/psicología , Estudios Retrospectivos , Estudios Prospectivos , SARS-CoV-2 , Ansiedad/psicología , Reino Unido/epidemiología
2.
BMC Gastroenterol ; 22(1): 160, 2022 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-35365084

RESUMEN

BACKGROUND: Non-traumatic hemoperitoneum was a rare event with the risk of sudden death. Spontaneous rupture of hepatocellular carcinoma is the most intuitive diagnosis when hemoperitoneum occurs in cirrhotic patients who are not regularly followed up. However, other etiologies of hemoperitoneum, such as intra-abdominal varix rupture, should be kept in mind. CASE PRESENTATION: A 44-year-old man with alcoholic liver cirrhosis, Child-Pugh B was sent to our emergency department (ED) because of recurrent abdominal pain and hypovolemic shock. He had similar symptoms one month ago and was diagnosed as hepatocellular carcinoma (HCC) rupture with hemoperitoneum, therefore he underwent trans-arterial embolization (TAE). However, the follow-up magnetic resonance imaging (MRI) showed less possibility of hepatocellular carcinoma. Contrast enhanced abdominal computed tomography (CT) showed possible umbilical vein contrast agent extravasation. Exploratory laparotomy confirmed the diagnosis of rupture umbilical varix with hemoperitoneum. CONCLUSION: Although umbilical varix rupture is a rare cause of hemoperitoneum, it should be kept in mind in cirrhotic patients with unexplained hemoperitoneum.


Asunto(s)
Carcinoma Hepatocelular , Neoplasias Hepáticas , Várices , Adulto , Carcinoma Hepatocelular/complicaciones , Hemoperitoneo/diagnóstico por imagen , Hemoperitoneo/etiología , Humanos , Neoplasias Hepáticas/complicaciones , Masculino , Rotura Espontánea/complicaciones , Rotura Espontánea/diagnóstico por imagen , Várices/complicaciones , Várices/diagnóstico por imagen
3.
Hong Kong Med J ; 28(2): 107-115, 2022 04.
Artículo en Inglés | MEDLINE | ID: mdl-35354666

RESUMEN

INTRODUCTION: Pelvic organ prolapse (POP) is common among older women. With the increasing lifespan and emphasis on quality of life worldwide, older women increasingly prefer surgical treatment for POP. We reviewed the surgical treatment of POP in older women to characterise its safety, effectiveness, and the type most often selected. METHODS: This multicentre, retrospective study was conducted at four hospitals between 2013 and 2018. Included patients were aged ≥75 years and had undergone POP surgery. We compared patient demographic characteristics, POP severity, and surgical outcomes between reconstructive and obliterative surgeries; these comparisons were also made among vaginal hysterectomy plus pelvic floor repair (VHPFR), transvaginal mesh surgery (TVM), vaginal hysterectomy (VH) plus colpocleisis, and colpocleisis alone. RESULTS: In total, 343 patients were included; 84.3% and 15.7% underwent reconstructive and obliterative surgeries, respectively. Overall, 246 (71.7%), 43 (12.5%), 20 (5.8%), and 34 (9.9%) patients underwent VHPFR, TVM, VH plus colpocleisis, and colpocleisis alone, respectively. Patients who were older (81.9 vs 79.6 y; P=0.001), had vault prolapse (38.9% vs 3.5%; P<0.001), and had medical co-morbidities (37% vs 4.8%; P<0.001) chose obliterative surgery more frequently than reconstructive surgery. Obliterative surgeries had shorter operative time (73.5 min vs 107 min; P<0.001) and fewer surgical complications (9.3% vs 28.0%; P=0.003). Vaginal hysterectomy plus pelvic floor repair had the highest rate of surgical complications (most were minor), while colpocleisis alone had the lowest rate (30.1% vs 8.8%; P=0.01). CONCLUSIONS: Pelvic organ prolapse surgeries were safe and effective for older women. Colpocleisis may be appropriate as primary surgery for fragile older women.


Asunto(s)
Procedimientos Quirúrgicos Ginecológicos , Prolapso de Órgano Pélvico , Anciano , Femenino , Hong Kong , Humanos , Prolapso de Órgano Pélvico/cirugía , Calidad de Vida , Estudios Retrospectivos , Mallas Quirúrgicas , Resultado del Tratamiento , Vagina/cirugía
4.
Acta Virol ; 64(4): 470-479, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33151741

RESUMEN

The methods for expansion of human cytomegalovirus (HCMV)-specific T lymphocytes are limited due to the complex culture process, long culture duration, and human leukocyte antigen (HLA) restriction. Here, we report that in vitro stimulation with pp65 kDa phosphoprotein (pp65)-derived overlapping synthetic peptides rapidly generates large numbers of HCMV-specific cytotoxic T lymphocytes from peripheral blood mononuclear cells (PBMCs) regardless of HLA type. Treatment of PBMCs from healthy volunteers expressing HLA-A*02:01 or HLA-A*24:02 with 138 pp65 overlapping peptides (OLP) resulted in an expansion of HCMV pp65 NLVPMVATV (NLV) pentamer-specific CD8+ T lymphocytes that expressed interferon (IFN)-γ, but the pp65 NLV peptide did not generate HCMV-specific CD8+ T lymphocytes in PBMCs obtained from an HLA-A*24:02 donor due to HLA restriction. The OLP-induced T lymphocytes specific for HCMV derived from PBMCs of HLA-A*02:01- and HLA-A*24:02-expressing donors showed effective cytolytic responses against target cells loaded with OLP or the NLV epitope, but pp65 NLV peptide-induced T lymphocytes did not. Phenotypic analyses demonstrated that OLP increased the frequency of CD3+ CD8+ cells, but not CD3+ CD4+, CD14+, or CD56+ cells, in donor PBMCs. Thus, this study provides evidence that in vitro stimulation with OLP efficiently generates sufficient numbers of HCMV pp65-specific cytotoxic T lymphocytes for adoptive cell therapy. Keywords: human cytomegalovirus; cytotoxic T lymphocyte; overlapping peptides; pp65; cytotoxicity.


Asunto(s)
Infecciones por Citomegalovirus/inmunología , Péptidos/inmunología , Linfocitos T Citotóxicos/virología , Proteínas de la Matriz Viral/inmunología , Citomegalovirus , Antígenos HLA-A , Humanos , Leucocitos Mononucleares , Fosfoproteínas/inmunología
5.
Anaesthesia ; 73(12): 1515-1523, 2018 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-30255929

RESUMEN

Refractory intra-operative cardiac arrest is a challenging issue for anaesthetists. In this study, we analysed the outcomes of adult patients who received extracorporeal cardiopulmonary resuscitation for refractory intra-operative cardiac arrest between 2005 and 2016, using data from our institutional extracorporeal membrane oxygenation registry. We defined refractory intra-operative cardiac arrest as the failure of a return of spontaneous circulation after 30 min of cardiopulmonary resuscitation. The primary outcome measure was neurologically intact survival with a cerebral performance category score of 1 or 2 at hospital discharge. Between 2005 and 2016, extracorporeal cardiopulmonary resuscitation was used to treat 23 patients who experienced refractory cardiac arrest in the operating room. The survival rates of neurologically-intact subjects were 9/23 (39%) and 6/23 (26%) at 24 h postoperatively and at hospital discharge, respectively. The main cause of refractory-intra-operative cardiac arrest was haemorrhagic shock in 13 out of 23 (57%) patients, and the neurologically-intact survival rate in these patients was 3/13 (23%) at discharge. Our study showed that approximately a quarter of patients with refractory intra-operative cardiac arrest caused by haemorrhage would receive survival benefit from extracorporeal cardiopulmonary resuscitation. Therefore, extracorporeal cardiopulmonary resuscitation may be a possible option in this clinically-challenging situation.


Asunto(s)
Reanimación Cardiopulmonar/métodos , Oxigenación por Membrana Extracorpórea/métodos , Paro Cardíaco/terapia , Complicaciones Intraoperatorias/terapia , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Paro Cardíaco/etiología , Humanos , Masculino , Persona de Mediana Edad , Enfermedades del Sistema Nervioso/etiología , Estudios Retrospectivos , Choque Hemorrágico/complicaciones , Choque Hemorrágico/terapia , Tasa de Supervivencia , Centros de Atención Terciaria , Resultado del Tratamiento , Adulto Joven
6.
Br J Cancer ; 109(1): 229-34, 2013 Jul 09.
Artículo en Inglés | MEDLINE | ID: mdl-23652313

RESUMEN

BACKGROUND: In addition to lung cancers, tuberculosis infections have been associated with increased risk of non-pulmonary malignancies in case reports. Our population-based study employed standardized incidence ratios (SIRs) to systemically survey non-pulmonary cancer risks after tuberculosis infections. METHODS: Data of patients who had newly diagnosed tuberculosis, were aged 20 years or older, and had no prior cancer or tuberculosis were sampled from the Taiwan National Health Insurance database between 2000 and 2010. SIRs compared cancer incidence in patients with tuberculosis infections to the general population. SIRs of specific cancers were further analyzed with respect to gender and time after tuberculosis infections. RESULTS: After a follow-up period of 28 866 person-years, 530 tuberculosis cases developed cancers compared with 256 cases in the general populations (2.07, 95% confidence interval (CI), 1.90-2.26). The SIR of non-pulmonary malignancies was also increased (1.71, 95% CI, 1.54-1.90). For males, SIRs were increased within 1 year after tuberculosis diagnosis for the following cancers: head and neck, esophageal, colorectal, liver, lung, melanomas, and Hodgkin's disease. SIRs were increased for liver, biliary, lung, and bladder cancers beyond the first year after tuberculosis diagnosis. For females, SIRs were increased for leukemia, esophageal, and lung cancers within the first year, and only for leukemia beyond 1 year post diagnosis. CONCLUSION: Having found increased risks of several cancers that differ with gender and time after tuberculosis diagnosis, physicians may consider these factors in patients following tuberculosis diagnosis.


Asunto(s)
Neoplasias/epidemiología , Tuberculosis/epidemiología , Adulto , Anciano , Estudios de Cohortes , Femenino , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Sistema de Registros , Factores de Riesgo , Factores Sexuales , Taiwán/epidemiología , Adulto Joven
7.
Eur J Clin Microbiol Infect Dis ; 32(9): 1211-20, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23553594

RESUMEN

Tigecycline (TG) has been shown to be active in vitro against Acinetobacter baumannii, although data on the clinical efficacy of TG alone or in combination for the treatment of infections due to multidrug-resistant A. baumannii (MDRAB) remain limited. The purpose of this study was to investigate the clinical outcomes of patients with healthcare-associated infections (HAIs) caused by MDRAB who were treated with imipenem/cilastatin and sulbactam, and TG alone or in combination with other antibiotics. A total of 386 patients with HAIs caused by MDRAB were retrospectively analyzed and grouped into TG and non-TG groups, depending on whether they received TG treatment. Of the 266 patients in the TG group, 108 were treated with TG alone and 158 were treated with TG in combination with ceftazidime, ceftriaxone, piperacillin/tazobactam, or a carbapenem. All 120 patients in the non-TG group were treated with imipenem/cilastatin and sulbactam. The primary outcome measure was 30-day mortality after TG treatment and the secondary outcome was clinical outcome. There were no significant differences in survival rates between the two groups. However, the rate of unfavorable outcome was significantly lower (p < 0.05) among patients in the TG group than among patients in the non-TG group. The most significant predictor of unfavorable outcome was sepsis, whereas TG treatment and microbial eradication were the most significant predictors of favorable outcomes. Our study represents the largest study of patients with MDRAB infection treated with TG and expands our understanding of the role of TG therapy alone or in combination with other agents for the treatment of HAI caused by MDRAB.


Asunto(s)
Infecciones por Acinetobacter/tratamiento farmacológico , Acinetobacter baumannii/efectos de los fármacos , Antibacterianos/uso terapéutico , Infección Hospitalaria/tratamiento farmacológico , Minociclina/análogos & derivados , Anciano , Ceftazidima/uso terapéutico , Ceftriaxona/uso terapéutico , Cilastatina/uso terapéutico , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Quimioterapia Combinada , Femenino , Humanos , Imipenem/uso terapéutico , Masculino , Minociclina/uso terapéutico , Piperacilina/uso terapéutico , Sulbactam/uso terapéutico , Tigeciclina , Resultado del Tratamiento
8.
Asian-Australas J Anim Sci ; 26(9): 1247-54, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-25049906

RESUMEN

The effects of Sheng Hua Tang (SHT) on uterine involution and ovarian activity were investigated in postpartum dairy cows. SHT (70 g) was given to dairy cows (n = 10) to evaluate its effects for five days from the first postpartum day. Postpartum cows fed with a basal diet without SHT were used as the control group (n = 10). Ultrasounds and blood tests were recorded for four weeks from postpartum day seven with a 3-d interval. The results showed that the areas and diameters of endometria were significantly (p<0.01) reduced in the group that received SHT compared to the control group on the seventh postpartum day. The group that received SHT had an intrauterine fluid volume mean of 1.2±0.6 cm(3), which was significantly lower than that of the control group, 2.3±0.8 cm(3) (p<0.01) on the 13th postpartum day. In addition, the uterine tension score was a mean of 1.0±0.0 in the group that received SHT, which was also significantly lower than that of the control group, 1.5±0.5 (p<0.01) on the 19th postpartum day. Taken together, the Chinese herbal medicine remedy, SHT, promoted uterine involution and ovarian activity in postpartum dairy cows.

9.
Food Chem ; 402: 134291, 2023 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-36155288

RESUMEN

Heterocyclic amines (HAs) and polycyclic aromatic hydrocarbons (PAHs)are widely distributed in foods.This study aims to extract PAHs and HAs from pork jerky simultaneously by QuEChERS for analysis by GC-MS/MS and UPLC-MS/MS, respectively. Also,the effects of flavoring materials and processing temperature on the formation of PAHs and HAswere studied. Acetonitrile containing 1% acetic acid possessed the highest extraction efficiency, with high accuracy and precision being attained forHAs and PAHs. Pork jerky roasted at 220℃ generated a higherPAHs content than180℃, but unaffected the HAs formation.Addition of sugarreduced formation ofboth HAs and PAHs during roasting, while soy sauce reduced somePAHs and promotedHAs formation. Incorporation of 0.5% curcumaorcinnamon powderinhibited HA formation with amore pronounced effect being shown by the latter,but neither inhibitedPAH formation. The correlation between HA and PAH formation was assessed by principle component analysis.


Asunto(s)
Hidrocarburos Policíclicos Aromáticos , Carne de Cerdo , Carne Roja , Animales , Porcinos , Hidrocarburos Policíclicos Aromáticos/análisis , Espectrometría de Masas en Tándem , Cromatografía Liquida , Carne Roja/análisis , Aminas/análisis , Aromatizantes/análisis , Acetonitrilos
10.
Infection ; 40(1): 19-26, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-21887526

RESUMEN

PURPOSE: Acinetobacter baumannii, Acinetobacter genomic species 3 (AGS 3), and Acinetobacter genomic species sensu Tjernberg and Ursing (AGS 13TU) are phenotypically indistinguishable and are often reported together as the A. baumannii complex (ABC). Few studies have investigated the difference in outcome caused by these different species, and all involved heterogeneous groups of patients. This study aimed to delineate whether there are differences in the clinical characteristics and outcome among patients with solid tumors and bacteremia caused by A. baumannii or two other non-baumannii ABC species (AGS 3 plus AGS 13TU). METHODS: Patients with solid tumors and ABC bacteremia over a period of 5 years in a medical center were identified. The patient data were retrospectively reviewed and analyzed. RESULTS: We identified 103 patients with ABC bacteremia during the study period. Bacteremia was due to A. baumannii in 30 patients, AGS 3 in 24 patients, and AGS 13TU in 49 patients. Among the 103 patients with ABC bacteremia, recent stay in the intensive care unit (ICU) (p = 0.008) was independently associated with the acquisition of A. baumannii bacteremia. Multivariate analysis revealed that bacteremia caused by A. baumannii (hazard ratio [HR] 2.990, 95% confidence interval [CI], 1.021-8.752, p = 0.046) and Acute Physiology and Chronic Health Evaluation (APACHE) II score ≥21 (HR 4.623, 95% CI 1.348-15.859, p = 0.015) were independent factors associated with 14-day mortality. CONCLUSIONS: Infection with A. baumannii and a high APACHE II score (≥21) might be associated with poor outcome in patients with solid tumors and ABC bacteremia.


Asunto(s)
Infecciones por Acinetobacter/mortalidad , Acinetobacter/genética , Bacteriemia/mortalidad , Neoplasias/mortalidad , Acinetobacter/clasificación , Acinetobacter/efectos de los fármacos , Acinetobacter/fisiología , Infecciones por Acinetobacter/complicaciones , Infecciones por Acinetobacter/tratamiento farmacológico , Infecciones por Acinetobacter/patología , Acinetobacter baumannii/clasificación , Acinetobacter baumannii/efectos de los fármacos , Acinetobacter baumannii/genética , Acinetobacter baumannii/fisiología , Anciano , Anciano de 80 o más Años , Bacteriemia/complicaciones , Bacteriemia/tratamiento farmacológico , Bacteriemia/patología , ADN Bacteriano/genética , ADN Espaciador Ribosómico/genética , Farmacorresistencia Bacteriana Múltiple , Electroforesis en Gel de Campo Pulsado , Femenino , Humanos , Masculino , Persona de Mediana Edad , Tipificación Molecular , Análisis Multivariante , Neoplasias/complicaciones , Neoplasias/tratamiento farmacológico , Neoplasias/patología , Reacción en Cadena de la Polimerasa , Pronóstico , Estudios Retrospectivos , Factores de Riesgo , Resultado del Tratamiento
11.
J Nanosci Nanotechnol ; 12(7): 5843-6, 2012 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-22966667

RESUMEN

The optical and electronic properties in an InGaP/InGaAIP multiple quantum well (MQW) grown by using molecular-beam epitaxy utilizing the digital alloy technique were investigated through temperature-dependent photoluminescence (PL) measurements and numerical calculations. The high-resolution transmission electron microscopy images showed that the sample clearly displayed the InGaP wells and the InGaAIP barriers and separate confinement heterostructure layers. The PL measurements at various temperatures were performed to investigate the interband transitions of the InGaP/InGaAIP MQW. The electronic subband energies and the wavefunctions in the InGaP/InGaAIP MQW at several temperatures were determined by using a finite element method employing the standard 8-band k x p Lagrangian. The numerical results for optical interband transition energies from the ground state electron subband to the ground state heavy-hole subband of the InGaP/InGaAIP MQW at various temperatures were in reasonable agreement with the excitonic transition energies observed in the PL measurements.

12.
Osteoporos Int ; 22(5): 1469-79, 2011 May.
Artículo en Inglés | MEDLINE | ID: mdl-20683709

RESUMEN

SUMMARY: Using human mesenchymal stem cells, we identified catechin from a panel of herbal ingredients and Chinese traditional compounds with the strongest osteogenic effects. Catechin increased alkaline phosphatase activity, calcium deposition, and mRNA expression of Runx2 and osteocalcin. We further clarified the signaling pathway that catechin mediated to stimulate osteogenesis. INTRODUCTION: Human mesenchymal stem cells (hMSCs), useful as a species specific cell culture system for studying cell lineage differentiation, were examined as a tool to identify novel herbal ingredients and Chinese traditional compounds for enhancing osteogenesis. METHODS: Immortalized and primary hMSCs were induced in osteogenic induction medium in the presence of a variety of herbal ingredients and Chinese traditional compounds and osteogenic differentiation was evaluated by histochemical assays and quantitative RT-PCR. RESULTS: Using immortalized hMSCs, we first identified catechin, 18ß-glycyrrhetinic acid, baishao, and danggui with osteogenic properties, which enhanced calcium deposition at the dose without significant cytotoxic effects. Primary hMSCs were then applied for confirming the osteogenic effects of catechin, which increased alkaline phosphatase activity, calcium deposition, and mRNA expression of Runx2 and osteocalcin. We further found the extracellular signal-regulated kinase (ERK) pathway was downregulated upon stimulation with catechin. Catechin increased the level and activity of protein phosphatases 2A (PP2A) that dephosphorylates ERK kinase (MEK) and ERK. Further, PP2A inhibitor, okadaic acid, abolished the effect of catechin-mediated inactivation of ERK and stimulation of osteogenesis. The blocking effect of okadaic acid on osteogenesis was further reversed by PD98059, a specific inhibitor of MEK. Co-immunoprecipitation revealed the association of PP2A to both MEK and ERK. CONCLUSIONS: These studies propose catechin enhanced osteogenesis by increasing the PP2A level that inhibits the MEK and ERK signaling in hMSCs. These results prove the concept of using hMSCs as a convenient tool for rapid and consistent screening of the osteogenic herbal ingredients and traditional Chinese compounds.


Asunto(s)
Catequina/farmacología , Células Madre Mesenquimatosas/efectos de los fármacos , Osteogénesis/efectos de los fármacos , Proteína Fosfatasa 2/metabolismo , Fosfatasa Alcalina/metabolismo , Calcio/metabolismo , Catequina/administración & dosificación , Diferenciación Celular/efectos de los fármacos , Células Cultivadas , Células Inmovilizadas , Relación Dosis-Respuesta a Droga , Regulación hacia Abajo/efectos de los fármacos , Evaluación Preclínica de Medicamentos/métodos , Medicamentos Herbarios Chinos/farmacología , Quinasas MAP Reguladas por Señal Extracelular/genética , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Estudios de Factibilidad , Humanos , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Sistema de Señalización de MAP Quinasas/fisiología , Células Madre Mesenquimatosas/citología , Células Madre Mesenquimatosas/enzimología , Osteogénesis/fisiología
13.
J Phys Chem A ; 120(27): 4565-7, 2016 07 14.
Artículo en Inglés | MEDLINE | ID: mdl-27412326
14.
J Chem Phys ; 134(3): 034314, 2011 Jan 21.
Artículo en Inglés | MEDLINE | ID: mdl-21261360

RESUMEN

Aromatic amino acids have large UV absorption cross-sections and low fluorescence quantum yields. Ultrafast internal conversion, which transforms electronic excitation energy to vibrational energy, was assumed to account for the photostability of amino acids. Recent theoretical and experimental investigations suggested that low fluorescence quantum yields of phenol (chromophore of tyrosine) are due to the dissociation from a repulsive excited state. Radicals generated from dissociation may undergo undesired reactions. It contradicts the observed photostability of amino acids. In this work, we explored the photodissociation dynamics of the tyrosine chromophores, 2-, 3- and 4-hydroxybenzoic acid in a molecular beam at 193 nm using multimass ion imaging techniques. We demonstrated that dissociation from the excited state is effectively quenched for the conformers of hydroxybenzoic acids with intramolecular hydrogen bonding. Ab initio calculations show that the excited state and the ground state potential energy surfaces change significantly for the conformers with intramolecular hydrogen bonding. It shows the importance of intramolecular hydrogen bond in the excited state dynamics and provides an alternative molecular mechanism for the photostability of aromatic amino acids upon irradiation of ultraviolet photons.


Asunto(s)
Hidroxibenzoatos/química , Teoría Cuántica , Termodinámica , Fluorescencia , Procesos Fotoquímicos
15.
Hong Kong Med J ; 16(2): 121-5, 2010 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-20354246

RESUMEN

OBJECTIVE: To study the efficacy and safety of endoscopic ultrasonography-guided fine-needle aspiration in the management of mediastinal diseases in Hong Kong. DESIGN: Retrospective review of prospectively collected data. SETTING: University teaching hospital, Hong Kong. PATIENTS: A total of 125 consecutive patients with various mediastinal and pulmonary lesions that underwent trans-oesophageal endoscopic ultrasonography-guided fine-needle aspiration from July 1998 to June 2007. MAIN OUTCOME MEASURES: The diagnostic accuracy and safety of the procedure and its influence in patient management. RESULTS: Malignancy was confirmed in 62 (50%) of the patients and excluded in 42 (34%). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of endoscopic ultrasonography-guided fine-needle aspiration in diagnosing mediastinal malignancies were 75% (95% confidence interval, 64-83%), 100% (90-100%), 100% (93-100%), 67% (54-78%), and 83%, respectively. Eighty-six (69%) of the patients had their initial plan of invasive investigations changed. Only one (0.8%) patient developed a septic complication in a mediastinal cyst after puncturing, and was treated surgically. CONCLUSIONS: Trans-oesophageal endoscopic ultrasonography-guided fine-needle aspiration is a minimally invasive, effective, and safe method of diagnosing malignant mediastinal disease. It may reduce the need for other invasive investigations.


Asunto(s)
Endosonografía/métodos , Enfermedades del Mediastino/diagnóstico , Neoplasias del Mediastino/diagnóstico , Adulto , Anciano , Anciano de 80 o más Años , Biopsia con Aguja/efectos adversos , Biopsia con Aguja/métodos , Endosonografía/efectos adversos , Femenino , Estudios de Seguimiento , Hospitales Universitarios , Humanos , Masculino , Enfermedades del Mediastino/patología , Neoplasias del Mediastino/patología , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Estudios Retrospectivos , Sensibilidad y Especificidad , Sepsis/etiología
16.
Opt Express ; 17(23): 20991-7, 2009 Nov 09.
Artículo en Inglés | MEDLINE | ID: mdl-19997337

RESUMEN

We demonstrate the enhancement of light extraction in 633 nm AlGaInP light-emitting diodes (LEDs) with antireflective subwavelength structures (SWS). From the contour plots by the rigorous coupled wave analysis method, it is found that the reduction of the internal reflection strongly depends on the period of SWS. The Ag nanoparticles formed by thermal dewetting were used as an etch mask for dry etch process to fabricate antireflective SWS on the LED surface. The tapered pillars on the GaP were fabricated, on average, with distances below 200 nm, satisfying the required antireflection condition at the emission wavelength. The improvement in light output power by approximately 26.4% was achieved for the fabricated AlGaInP LEDs with SWS compared to the conventional LEDs due to a strongly reduced Fresnel internal reflection at the GaP/air interface. The improved directionality in the far-field pattern was also obtained due to the directional light extraction enhancement.

17.
Science ; 236(4803): 793-8, 1987 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-17777849

RESUMEN

The experimental investigation of elementary chemical reactions is presently in a very exciting period. The advance in modern microscopic experimental methods, especially crossed molecular beams and laser technology, has made it possible to explore the dynamics and mechanisms of important elementary chemical reactions in great detail. Through the continued accumulation of detailed and reliable knowledge about elementary reactions, we will be in a better position to understand, predict, and control many time-dependent macroscopic chemical processes that are important in nature or to human society. In addition, because of recent improvements in the accuracy of theoretical predictions based on large-scale ab initio quantum mechanical calculations, meaningful comparisons between theoretical and experimental findings have become possible. In the remaining years of the 20th century, there is no doubt that the experimental investigation of the dynamics and mechanisms of elementary chemical reactions will play a very important role in bridging the gap between the basic laws of mechanics and the real world of chemistry.

18.
Science ; 274(5292): 1508-11, 1996 Nov 29.
Artículo en Inglés | MEDLINE | ID: mdl-8929407

RESUMEN

The reaction of ground-state carbon atoms with acetylene was studied under single-collision conditions in crossed beam experiments to investigate the chemical dynamics of forming cyclic and linear C3H isomers (c-C3H and l-C3H, respectively) in interstellar environments via an atom-neutral reaction. Combined state-of-the-art ab initio calculations and experimental identification of the carbon-hydrogen exchange channel to both isomers classify this reaction as an important alternative to ion-molecule encounters to synthesize C3H radicals in the interstellar medium. These findings strongly correlate with astronomical observations and explain a higher [c-C3H]/[l-C3H] ratio in the dark cloud TMC-1 than in the carbon star IRC+10216.


Asunto(s)
Astronomía , Carbono/química , Polvo Cósmico , Hidrocarburos/química , Hidrógeno/química , Acetileno/química , Fenómenos Astronómicos , Isomerismo
19.
Science ; 279(5354): 1181-4, 1998 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-9469802

RESUMEN

The reaction of hydrogen sulfide with ground-state atomic carbon was examined with crossed molecular beams experiments and ab initio calculations. The thiohydroxycarbene molecule, HCSH, was the reactive intermediate, which fragmented into atomic hydrogen and the thioformyl radical HCS. This finding may account for the unassigned HCS source and an unidentified HCSH radical needed to match observed CS abundances from the collision of comet Shoemaker-Levy 9 into Jupiter. In the shocked jovian atmosphere, HCS could further decompose to H and CS, and CS could react with SH and OH to yield the observed CS2 and COS.


Asunto(s)
Carbono/química , Radicales Libres/química , Sulfuro de Hidrógeno/química , Júpiter , Meteoroides , Sulfuros/química , Atmósfera , Compuestos Inorgánicos de Carbono/química , Disulfuro de Carbono/química , Medio Ambiente Extraterrestre , Óxidos de Azufre/química
20.
Science ; 269(5220): 57-9, 1995 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-17787703

RESUMEN

The dynamics of the carbonium ion (CH(5)(+)), a highly reactive intermediate with no equilibrium structure, was studied by measuring the infrared spectra for internally cold CH(5)(+)(H(2))n(n = 1, 2, 3) stored in an ion trap. First-principle molecular dynamics methods were used to directly simulate the internal motion for these ionic complexes. The combined experimental and theoretical efforts substantiated the anticipated scrambling motion in the CH(5)(+) core and revealed the effect of the solvent molecular hydrogen in slowing down the scrambling. The results indicate the feasibility of using solvent molecules to stabilize the floppy CH(5)(+) ion in order to make it amenable to spectroscopic study.

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