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1.
BMJ Case Rep ; 17(1)2024 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-38238164

RESUMO

Cutaneous amebiasis is a rare clinical entity caused by the invasive protozoan parasite Entamoeba histolytica that can be readily diagnosed with skin biopsy if suspected. It presents as a rapidly progressive and destructive ulceration with necrosis. A man in his 40s with metastatic rectal cancer who underwent palliative abdominal perineal resection with end colostomy in his left lower quadrant and on systemic chemotherapy developed progressive breakdown of his peristomal skin unresponsive to antibiotics that was then diagnosed to be cutaneous amebiasis. It is important to be aware of cutaneous amebiasis and include it in the differential diagnosis when peristomal wounds do not respond to treatment.


Assuntos
Amebíase , Entamoeba histolytica , Dermatopatias Parasitárias , Masculino , Humanos , Colostomia , Amebíase/diagnóstico , Antibacterianos/uso terapêutico , Úlcera , Dermatopatias Parasitárias/diagnóstico
2.
South Asian J Cancer ; 11(4): 361-369, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36756098

RESUMO

Supriya MallickIntroduction Malignant gliomas are the most common primary malignant brain tumors and are typically treated with maximal safe surgical resection followed by chemoradiation. One of the unintended effects of radiation is depletion of circulating lymphocyte pool, which has been correlated with inferior overall survival outcomes. Methods A comprehensive and systematic searches of the PubMed, Cochrane Central, and Embase databases were done to assess the studies that have reported radiation-related lymphopenia in high-grade gliomas. Hazard ratios (HRs), odds ratios (OR), and mean differences were represented with Forest plots comparing patients with severe lymphopenia and no severe lymphopenia. Review Manager Version 5.3 (The Nordic Cochrane Centre, Copenhagen, Denmark) was used for the analysis. Results Nineteen studies were included in the final systematic review and 12 studies were included in the meta-analysis. The odds of developing severe lymphopenia were 0.39 (95% CI:0.19, 0.81, I 2 = 94%, p = 0.01). Patients with severe lymphopenia were at increased risk of death with a pooled HR = 2.19 (95% CI: 1.70, 2.83, I 2 = 0%, p <0.00001) compared to patients with no severe lymphopenia. The mean difference in survival between patients with severe lymphopenia and no severe lymphopenia was -6.72 months (95% CI: -8.95, -4.49, I 2 = 99%, p <0.00001), with a better mean survival in the no severe lymphopenia group. Conclusion Radiation-induced severe lymphopenia was associated with poor overall survival and increased risk of death. Photon therapy, larger planning target volume, higher brain dose, higher hypothalamus dose, and female gender were associated with increased risk of severe lymphopenia.

3.
J Biomed Nanotechnol ; 15(8): 1714-1723, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31219010

RESUMO

In this study, we have synthesized and characterized a pure boron nanoparticle containing asolectin phospholipid-based liposome construct prepared using a water-in-oil emulsion method, as a novel alternative agent for BNCT, which contain poly(maleic anhydride-alt-1-octadecene) (PMAO) and polyethylene glycol (PEG) on the surface, and Cy5 near infrared (NIR) fluorescent dye and boron nanoparticles in the core (3PCB). A tumor-specific targeting ligand, folic acid (FA), was conjugated to PEG to produce a folate-functionalized liposome (FA-3PCB) for improved targeted delivery and accumulation of boron in cancer cells. The liposomes showed an average diameter of 100-120 nm and zeta potential of -38.0±1.5 mV. Cellular uptake monitored by fluorescence microscopy confirmed the targeting capability of FA-conjugated liposomes. Accumulation of FA-conjugated liposomes in C6-brain tumor cells was much higher than that of non-FA conjugated liposomes under the same conditions. ICP-MS (Inductively Coupled Plasma Mass Spectrometry) quantification confirmed that boron accumulated in cancer cells to sufficient intracellular concentration for therapeutic benefit from BNCT. These liposomes show blood-brain barrier (BBB) crossing ability, low cytotoxicity, and excellent stability under physiological conditions. Thus, these liposomes are a promising new boron carrier for BNCT.


Assuntos
Terapia por Captura de Nêutron de Boro , Nanopartículas , Boro , Ácido Fólico , Lipossomos
4.
Int J Radiat Oncol Biol Phys ; 105(1): 73-86, 2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-30797890

RESUMO

PURPOSE: To identify predictors of radiation-induced liver disease (RILD) in patients with hepatocellular carcinoma (HCC) treated with proton beam therapy (PBT). METHODS: This multicenter study included 136 patients with HCC (eastern, n = 102; western, n = 34) without evidence of intrahepatic tumor progression after PBT. The RILD was defined as ascites with alkaline-phosphatase abnormality, grade ≥3 hepatic toxicity, or Child-Pugh score worsening by ≥2 within 4 months after PBT completion. The proton doses were converted to equivalent doses in 2-GyE fractions. The unirradiated liver volume (ULV) was defined as the absolute liver volume (LV) receiving <1 GyE; the standard liver volume (SLV) was calculated using body surface area. Possible correlations of clinicodosimetric parameters with RILD were examined. RESULTS: The mean pretreatment LV was 85% of SLV, and patients with a history of hepatectomy (P < .001) or hepatitis B virus infection (P = .035) had significantly smaller LV/SLV. Nineteen (14%) patients developed RILD. Multivariate logistic regression analysis identified ULV/SLV (P = .001), gross tumor volume (P = .001), and Child-Pugh classification (P = .002) as independent RILD predictors, and mean liver dose and target-delivered dose were not associated with RILD occurrence. A "volume-response" relationship between ULV/SLV and RILD was consistently observed in both eastern and western cohorts. In Child-Pugh class-A patients whose ULV/SLV were ≥50%, 49.9%-40%, 39.9%-30% and <30%, the RILD incidences were 0%, 6%, 16%, and 39% (P < .001), respectively. For the Child-Pugh class-B group, the RILD incidences in patients with ≥60%, 59.9%-40%, and <40% of ULV/SLV were 0%, 14%, and 83% (P = .006), respectively. CONCLUSIONS: The ULV/SLV, not mean liver dose, independently predicts RILD in patients with HCC undergoing PBT. The relative and absolute contraindications for Child-Pugh class-A patient's ULV/SLV are <50% and <30%, and <60% and <40% for Child-Pugh class-B patients, respectively. Our results indicate that the likelihood of hepatic complications for PBT is dictated by similar metrics as that for surgery.


Assuntos
Carcinoma Hepatocelular/radioterapia , Hepatopatias/etiologia , Neoplasias Hepáticas/radioterapia , Fígado/efeitos da radiação , Terapia com Prótons/efeitos adversos , Idoso , Idoso de 80 Anos ou mais , Fosfatase Alcalina/sangue , Análise de Variância , Ascite/etiologia , Feminino , Hepatectomia , Hepatite B/patologia , Humanos , Fígado/patologia , Masculino , Tamanho do Órgão , Tolerância a Radiação , Dosagem Radioterapêutica , Análise de Regressão , Estudos Retrospectivos
5.
Cancer Rep (Hoboken) ; 2(2): e1152, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-32721134

RESUMO

OBJECTIVE: Cancer survivorship has thrown the spotlight on the incidence of nonmalignant chronic diseases in cancer patients. Endothelial injury is increasingly recognized as a consequence of cancer treatment, particularly after radiation therapy (RT). This review is to provide a current understanding on the pathophysiological mechanisms and predictive biomarkers of radiation-induced vascular injury. RECENT FINDINGS: Radiation directly impacts vasculature by causing endothelial apoptosis and senescence, and alterations in normal homeostasis. This altered milieu at the endothelial surface may contribute to a systemic chronic inflammatory state that is superimposed upon the cascade of normal senescence processes leading to acceleration of age-related disorders, atherosclerosis, and chronic fibrosis. Vasculature imaging, blood-based or cell-component biomarkers, and signatures of genomics, proteomics, metabolomics, and radiomics are potential tools for detection of vascular damage after irradiation. CONCLUSIONS: Development of a valid prediction model by combining an array of imaging tools, blood-based biomarkers, coupled with novel predictors like exosomes and metabolic degradation products can serve to identify RT-induced vascular injury early for subsequent introduction of newer therapeutic approaches to counter radiation morbidity.


Assuntos
Neoplasias/radioterapia , Lesões por Radiação/diagnóstico , Lesões por Radiação/etiologia , Lesões do Sistema Vascular/diagnóstico , Lesões do Sistema Vascular/etiologia , Animais , Biomarcadores/análise , Biomarcadores/metabolismo , Genômica/métodos , Humanos , Metabolômica/métodos , Neoplasias/patologia , Lesões por Radiação/metabolismo , Lesões do Sistema Vascular/metabolismo
6.
Adv Mater ; 29(12)2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28128879

RESUMO

Vertical stacking and lateral growth of molybdenum disulfide (MoS2 ) are controlled with remarkable precision, and MoS2 nanotubes are directly converted from nanofibers. Predictive synthesis is enabled by identifying the specific thermodynamic region where the Boudouard reaction becomes favored. It reveals how the chemical potential of each species in the MoSCO system can predict phase behaviors.

7.
Nat Commun ; 7: 12449, 2016 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-27527268

RESUMO

Interfaces, such as grain boundaries in a solid material, are excellent regions to explore novel properties that emerge as the result of local symmetry-breaking. For instance, at the interface of a layered-chalcogenide material, the potential reconfiguration of the atoms at the boundaries can lead to a significant modification of the electronic properties because of their complex atomic bonding structure. Here, we report the experimental observation of an electron source at 60° twin boundaries in Bi2Te3, a representative layered-chalcogenide material. First-principles calculations reveal that the modification of the interatomic distance at the 60° twin boundary to accommodate structural misfits can alter the electronic structure of Bi2Te3. The change in the electronic structure generates occupied states within the original bandgap in a favourable condition to create carriers and enlarges the density-of-states near the conduction band minimum. The present work provides insight into the various transport behaviours of thermoelectrics and topological insulators.

8.
Materials (Basel) ; 7(3): 1520-1538, 2014 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-28788529

RESUMO

Shape memory behavior of crystalline shape memory polyurethane (SPU) reinforced with graphene, which utilizes melting temperature as a shape recovery temperature, was examined with various external actuating stimuli such as direct heating, resistive heating, and infrared (IR) heating. Compatibility of graphene with crystalline SPU was adjusted by altering the structure of the hard segment of the SPU, by changing the structure of the graphene, and by changing the preparation method of the graphene/SPU composite. The SPU made of aromatic 4,4'-diphenylmethane diisocyanate (MSPU) exhibited better compatibility with graphene, having an aromatic structure, compared to that made of the aliphatic hexamethylene diisocyanate. The finely dispersed graphene effectively reinforced MSPU, improved shape recovery of MSPU, and served effectively as a filler, triggering shape recovery by resistive or IR heating. Compatibility was enhanced when the graphene was modified with methanol. This improved shape recovery by direct heating, but worsened the conductivity of the composite, and consequently the efficiency of resistive heating for shape recovery also declined. Graphene modified with methanol was more effective than pristine graphene in terms of shape recovery by IR heating.

9.
J Cardiol ; 62(2): 131-7, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23731925

RESUMO

BACKGROUND: Augmentation index (AIx) and pulse pressure amplification (PPA, here the aortic/brachial pulse pressure ratio) are an age-related emerging risk factor for cardiovascular disease. However, it has not been clearly shown that AIx and PPA predict a high risk of coronary artery disease (CAD). OBJECTIVES: The aim of the study was to investigate the association between non-invasively measured aortic wave reflection (AWR) and PPA and CAD. METHODS: The study group consisted of 80 patients who were admitted to our institute for elective coronary angiography. We non-invasively measured augmentation pressure (AP), AIx, and PPA using radial applanation tonometry. RESULTS: When the extent of CAD was divided by no or minimal CAD, 1- or 2- and 3-vessel disease (VD), there was a significant association between the extent of CAD and AIx and PPA in patients aged <65 years, but not in patients aged ≥ 65 years. In multivariate regression analysis after controlling the traditional risk factors, the odds ratio of having 3VD was significant in patients aged <65 years: 2.15 (1.04-4.44; p=0.039) per 5% increase of AIx and 2.02 (1.15-3.55; p=0.015) per 0.05 increase of PPA, but not in patients aged ≥ 65 years. The severity of CAD expressed as a Gensini score showed a significant correlation with AP, AIx, and PPA in patients aged <65 years, but not in patients aged ≥ 65 years. CONCLUSION: Increasing of non-invasively measured AWR and PPA is related to the severity of CAD, particularly in younger patients up to 65 years of age.


Assuntos
Aorta/fisiopatologia , Pressão Arterial/fisiologia , Artéria Braquial/fisiopatologia , Doença da Artéria Coronariana/diagnóstico , Doença da Artéria Coronariana/fisiopatologia , Análise de Onda de Pulso , Fatores Etários , Idoso , Biomarcadores , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Risco , Índice de Gravidade de Doença
10.
Korean Circ J ; 42(11): 776-80, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23236331

RESUMO

Primary cardiac lymphoma (PCL) is a rare disorder, but the incidence is increasing and its clinical manifestations are various. We report a case of PCL, which mimics an acute coronary and aortic syndrome. A 51 year-old female was presented with chest pain radiating to the back. Her initial electrocardiogram revealed T wave inversion in the leads of V 5-6, II, III and aVF. Additionally, cardiac troponin-T was slightly elevated. Chest radiography showed marked mediastinal widening. Computed tomography scan showed a huge pericardial mass. The histopathologic findings of the mass were compatible with diffuse large B cell lymphoma. She died of refractory ventricular tachycardia, probably, due to an extensive infiltration of PCL to the myocardium.

11.
J Nanosci Nanotechnol ; 12(11): 8420-30, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23421225

RESUMO

A functionalized graphene sheet (FGS), which was prepared by the thermal reduction of graphite oxide, was modified by oxidation with H2O2. Elemental analysis, X-ray photoelectron spectroscopy, and Fourier transform infrared (FTIR) spectroscopy showed that additional oxygen functional groups, either doubly or singly bound to carbon, were created by the oxidation. The size and electrical conductivity of the FGS were reduced by the oxidation. During FGS/Polycaprolactone (PCL) nanocomposite preparation by an in situ polymerization method, PCL was grafted onto a FGS by chain growth from a functional group on FGS such as hydroxyl. Thermogravimetry and FTIR spectra demonstrated that the amount of grafted polycaprolactone (PCL) was decreased by the oxidation of FGS, suggesting that PCL chain growth from the FGS surface was inhibited by the neighboring carboxylic acid group on the FGS. Enhanced compatibility between the oxidized FGS and the PCL matrix was observed by optical microscopy and scanning electron microscopy. The reinforcing effect on tensile properties was also enhanced by the oxidized FGS in the FGS/PCL nanocomposites. This suggests that the surface coverage by the grafted PCL chains on the oxidized FGS is higher than that on a pristine FGS, although the grafted PCL chain length is shorter and the amount grafted is smaller.


Assuntos
Cristalização/métodos , Grafite/química , Peróxido de Hidrogênio/química , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Oxigênio/química , Poliésteres/química , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Oxirredução , Tamanho da Partícula , Propriedades de Superfície
12.
J Gastroenterol Hepatol ; 25(6): 1105-10, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20594226

RESUMO

BACKGROUND: Sphingolipids play a very important role in cell membrane formation, signal transduction and plasma lipoprotein metabolism. The first rate-limiting step in the sphingolipid biosynthetic pathway is catalyzed by serine palmitoyltransferase (SPT), and myriocin is a potent and specific inhibitor of SPT. We investigated the impact of SPT inhibition on cholesterol gallstone formation in C57BL/6J mice. METHODS: Three groups of eight-week-old C57BL/6J mice were utilized. Each group consisted of 20 mice; group A, B, and C were fed normal chow, lithogenic diet with phosphate buffered saline, and lithogenic diet with myriocin (0.3 mg/kg), respectively, for 6 weeks. The ceramide levels in both serum and bile were assessed by high performance liquid chromatography analysis. Protein expression of ERK, JNK and p38 in the extracted gallbladder were determined by Western-blot analysis. RESULTS: Myriocin treatment caused a significant decrease in the rate of cholesterol gallstone formation. The lithogenic diet mice (group B) showed the highest ceramide activities in both the serum and bile among all the tested groups and there was significant suppression of the ceramide levels in both the serum and bile of the myriocin-treated mice (group C, p < 0.05). Phosphorylation of p38 in the gallbladder was increased in the lithogenic-diet mice and the expression of phosphorylated p38 was significantly suppressed in the myriocin treated mice. CONCLUSIONS: SPT inhibition by myriocin suppressed gallstone formation and the levels of ceramide in both the serum and bile. p38 in the cellular signaling pathways might be associated with cholesterol gallstone formation.


Assuntos
Colesterol/metabolismo , Ácidos Graxos Monoinsaturados/administração & dosagem , Cálculos Biliares/tratamento farmacológico , Imunossupressores/administração & dosagem , Esfingolipídeos/antagonistas & inibidores , Animais , Bile/metabolismo , Western Blotting , Ceramidas/metabolismo , Cromatografia Líquida de Alta Pressão , Modelos Animais de Doenças , MAP Quinases Reguladas por Sinal Extracelular/biossíntese , Vesícula Biliar/metabolismo , Cálculos Biliares/induzido quimicamente , Cálculos Biliares/metabolismo , Proteínas Quinases JNK Ativadas por Mitógeno/biossíntese , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Esfingolipídeos/biossíntese , Resultado do Tratamento , Triglicerídeos/sangue
13.
Ind Health ; 46(4): 397-403, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18716389

RESUMO

We report findings regarding otolaryngologist-confirmed rhinitis, current exposure to MWF aerosols, fungi, and endotoxins for workers in a plant manufacturing automobile piston rings. Questionnaire data showed that 61.5% of 187 workers exhibited rhinitis-related symptoms. Rhinitis was confirmed in 99 of 115 workers whom were medically examined. Otolaryngologist-confirmed rhinitis was present in 10 of 19 grinding workers (52.6%), 67 of 142 production workers (47.2%), and 22 of 26 quality control (QC) workers (84.6%). These rates are much higher than the rates of rhinitis-related symptoms in automobile plants and other occupational settings and quite high even allowing for the common occurrence of rhinitis in the general population. We found that rhinitis could develop even in workers exposed to less than 0.5mg/m(3) MWF aerosol. The average exposure to fungi exceeded 10 x 10(3) CFU/m(3), a level higher than that reported for other automobile plants. Although we were unable to identify significant risk factors for rhinitis using only the physician-confirmed rhinitis cases, this study concludes that exposure to MWF aerosol, which would include microbes and metals, could contribute to a high occurrence of rhinitis in grinding and production workers. Forty-nine workers (63.6%) of 77 rhinitis patients in grinding and production operations were determined to handle synthetic MWF directly. For QC workers, for whom the prevalence of physician-confirmed rhinitis was highest, exposure to a low level of MWF aerosol, including specific microbe species we couldn't identify, bright light, dry air, and certain work characteristics during inspection are possible risk factors for development of rhinitis. Further studies including identification of fungi species should be conducted so a firm conclusion can be made regarding the development of rhinitis in QC manufacturing plant workers.


Assuntos
Exposição Ocupacional , Rinite/epidemiologia , Adulto , Aerossóis , Automóveis , Feminino , Humanos , Indústrias , Coreia (Geográfico)/epidemiologia , Masculino , Pessoa de Meia-Idade , Rinite/diagnóstico , Rinite/etiologia , Inquéritos e Questionários
14.
J Occup Health ; 50(2): 212-20, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18403875

RESUMO

The main objective of this study was to determine the association between synthetic metalworking fluid (MWF) and rhinitis-related symptoms. At a plant manufacturing piston rings for automobiles, we interviewed grinders (19) and manufacturing workers (142) in operations where synthetic or semisynthetic MWF is handled, and administrative office workers (44) regarding the principal symptoms of rhinitis (nasal stuffiness, runny nose, anosmia, nasal itchiness, rhinorrhea, headache, epistaxis, and post-nasal drip). In addition, we assessed the current exposure of workers handling MWF to MWF aerosols, fungi, and endotoxins. Logistic regression analysis was used to examine the association between MWF surrogates indicative of MWF exposure and each rhinitis-related nasal symptom. Odds ratios (ORs) and 95% confidence intervals were adjusted for sex, age, smoking habit, and duration of employment. Among grinders handling synthetic MWF, the frequency of complaints of the dominant symptoms was 66.7% for nasal stuffiness, 77.8% for anosmia, 77.8% for runny nose, and 50.0% for headache. These rates are quite high even allowing for the common occurrence of rhinitis in the general population. Twenty eight of 34 grinding and manufacturing workers (82.4%) sampled were exposed to MWF mist above the threshold limit of 0.2 mg/m(3) listed as a notice of intended change by the American Conference for Governmental Industrial Hygienists (ACGIH). The percentage of workers exposed to MWF mist >0.5 mg/m(3) was 17.6%. Most workers were exposed to fungi levels >103 CFU/m(3). All exposures to endotoxins were <50 EU/m(3). Logistic regression analysis found that use of synthetic MWF was significantly associated with excess risk of nasal stuffiness (OR 3.5), nasal itchiness (OR 2.0), and runny nose (OR 2.1). The use of semi-synthetic MWF had little or no impact on the risk of developing rhinitis-related nasal symptoms. Grinding workers handling synthetic MWF had an increased risk of nasal stuffiness (OR 7.9), anosmia (OR 23.2), nasal itchiness (OR 8.3), runny nose (OR 20.4), post nasal drip (OR 18.4), and headache (OR 7.4) compared to administrative workers. Synthetic MWF may play an important role in the development of the dominant symptoms of rhinitis. Further study is needed to establish the risk of rhinitis or rhinitis-related symptoms according to MWF type.


Assuntos
Exposição por Inalação/efeitos adversos , Metalurgia , Doenças Profissionais/etiologia , Exposição Ocupacional/efeitos adversos , Rinite/etiologia , Adulto , Poluentes Ocupacionais do Ar/efeitos adversos , Estudos de Casos e Controles , Relação Dose-Resposta a Droga , Endotoxinas/análise , Feminino , Fungos/isolamento & purificação , Humanos , Óleos Industriais/intoxicação , Lubrificantes/intoxicação , Masculino , Pessoa de Meia-Idade , Doenças Profissionais/induzido quimicamente , Doenças Profissionais/epidemiologia , Rinite/induzido quimicamente , Rinite/epidemiologia , Fatores de Risco , Fumar/efeitos adversos , Inquéritos e Questionários
15.
Chemphyschem ; 9(1): 141-6, 2008 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-18080257

RESUMO

The low surface energy and the great immiscibility of poly (dimethylsiloxane) (PDMS) with liquid crystals (LCs) are used in the fabrication of holographic polymer dispersed liquid crystals (HPDLCs). By adding increasing amounts of PDMS, the extent of the phase separation between the polymer and the LC, the LC channel width, and-eventually-also the diffraction efficiency of the film can be increased, while keeping the droplet size essentially the same. In addition, the presence of PDMS causes a decrease in the switching voltage and an increase in the response time. At an optimum content of PDMS (PUA40), a minimum switching voltage of 4 V microm(-1), a rise time of 0.20 ms, and a decay of 14.75 ms were obtained. Regarding the effect of the LC content, an overshoot of the diffraction efficiency was observed when the amount of LC exceeded 35 %, which can be attributed to droplet coalescence.


Assuntos
Físico-Química/métodos , Dimetilpolisiloxanos/química , Cristais Líquidos/química , Polímeros/química , Silicones/química , Siloxanas/química , Difusão , Microscopia Eletrônica de Varredura , Peso Molecular , Óptica e Fotônica , Propriedades de Superfície , Fatores de Tempo
16.
Chemphyschem ; 8(1): 175-80, 2007 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-17146810

RESUMO

Effects of octanoic acid (OA) on the morphology, diffraction efficiency, and electro-optic properties of the transmission mode of holographic polymer-dispersed liquid crystals (HPDLC) are studied. Droplet size decreases with increasing OA content (0-9 %), and this leads to a monotonic increase in off-state diffraction with increasing OA content. However, on-state diffraction decreases with increasing applied voltage and shows a minimum at 6 % OA, for which minimum switching voltage (5 V microm(-1)) and maximum contrast ratio (10) are obtained. Rise time and decay time decrease with increasing OA content. Interposition of OA between polymer and LC droplet is theoretically predicted by the spreading coefficient (lambda>0) calculated on the basis of the solubility parameter, while the coalescence behavior of droplets is described by a dimensionless group (gamma d rho / mu(2)) called coalescence number.

17.
Chemphyschem ; 7(9): 2008-14, 2006 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-16892464

RESUMO

Transmission gratings of holographic polymer-dispersed liquid crystals (HPDLC) are prepared under controlled reaction conditions by adding various amounts of chain-transfer agent (CTA). The resulting films have a higher gel content with lower cross-link density, less dark reaction, less grating shrinkage with much smoother LC/polymer interfaces, smaller induction period, and fast saturation of diffraction efficiency, which shows a maximum of 95 % with 1 % CTA. An optimum LC content of 35 % is verified on the basis of morphology and reaction kinetics.

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