All-optical high-sensitivity resonant photoacoustic sensor for remote CH4 gas detection.

This paper presents an all-optical high-sensitivity resonant photoacoustic (PA) sensor to realize remote, long-distance and space-limited trace gas detection. The sensor is an integration of a T-type resonant PA cell and a particular cantilever-based fiber-optic acoustic sensor. The finite element simulations about the cantilever vibration mode and the PA field distributions are carried out based on COMSOL. The all-optical high-sensitivity resonant PA sensor, together with a high-speed spectrometer and a DFB laser source, makes up of a photoacoustic spectroscopy (PAS) system which is employed for CH4 detection. The measured sensitivity is 0.6 pm/ppm in the case of 1000 s average time, and the minimum detection limit (MDL) reaches 15.9 parts per billion (ppb). The detective light source and the excitation light source are all transmitted by optical fibers, therefore remote and long-distance measurement of trace gas can be realized. Furthermore, the excitation light source and the acoustic sensor are designed at the same side of the PA cell, the sensor may be used for space-limited trace gas detection.

Ppb-level detection of methane based on an optimized T-type photoacoustic cell and a NIR diode laser.

This paper presents an optimized T-type resonant photoacoustic (PA) cell for methane (CH4) gas detection. The noise transmission coefficients and PA field distributions of the T-type resonant PA cell have been evaluated using the finite element method and thermoviscous acoustic theory. The optimized T-type resonant PA cell, together with a near-infrared (NIR) distributed feedback (DFB) laser source, a high-speed spectrometer and a fiber-optic acoustic sensor constitutes a PAS system for CH4 detection. The sensitivity is measured to be 1.8 pm/ppm and a minimum detectable limit (MDL) of 9 parts per billion (ppb) can be achieved with an averaging time of 500 s. The optimized T-type longitudinal resonant PA cell features of high PA cell constant, fast response time and simple manufacturing process.

Ultrahigh Proton Conduction in Two Highly Stable Ferrocenyl Carboxylate Frameworks.

Nowadays, although research of proton conductive materials has been extended from traditional sulfonated polymers to novel crystalline solid materials such as MOFs, COFs, and HOFs, research on crystalline ferrocene-based carboxylate materials is very limited. Herein, we selected two hydrogen-bonded and π-π interactions-supported ferrocenyl carboxylate frameworks (FCFs), [FcCO(CH2)2COOH] (FCF 1) and [FcCOOH] (FCF 2) (Fc = (η5-C5H5)Fe(η5-C5H4)) to fully investigate their water-mediated proton conduction. Their excellent thermal, water, and chemical stabilities were confirmed by the means of thermogravimetric analyses, PXRD, and SEM determinations. The two FCFs indicate temperature- and humidity-dependent proton conductive features. Intriguingly, their ultrahigh proton conductivities are 1.17 × 10-1 and 1.01 × 10-2 S/cm, respectively, under 100 °C and 98% RH, which not only are comparable to the commercial Nafion membranes but also rank among the highest performing MOFs, HOFs, and COFs ever described. On the basis of the structural analysis, calculated Ea value, H2O vapor adsorption, PXRD, and SEM measurements, reasonable conduction mechanisms are highlighted. Our research provides a novel inspiration for finding new high proton conducting crystalline solid materials. Importantly, the outstanding conducting performance of 1 and 2 suggests their, hopefully, potential in fuel cells and related electrochemical fields.

Circulating APP, NCAM and Aß serve as biomarkers for Alzheimer's disease.

Alzheimer's disease (AD) is the most common neurodegenerative disease and the early diagnosis and intervention are important for valid treatment of AD. However, there are few biomarkers for the diagnosis and monitoring of AD. In the present study, circulating APP, NCAM, Aß40, and Aß42 were measured in order to identify which marker or combination of markers could be useful, cost-effective and noninvasive biomarkers for diagnosing and continuously monitoring AD. The results showed that circulating APP, NCAM, Aß40, and Aß42 were different between the AD group and the control group. Importantly, the combination of the four biomarkers had the highest AUC (0.997) with the highest sensitivity (98.5). Therefore, circulating APP, NCAM, Aß40, and Aß42 can be used as desirable biomarkers for AD diagnosis and monitoring.

Synergic interaction between amyloid precursor protein and neural cell adhesion molecule promotes neurite outgrowth.

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases worldwide. The main features of AD are the pathological changes of density and distribution of intracellular neurofibrillary tangles (NFT) and extracellular amyloid plaques. The processing of amyloid beta precursor protein (APP) to ß-amyloid peptide (Aß) is one of the critical events in the pathogenesis of AD. In this study, we evaluated the role of the interaction of neural cell adhesion molecule (NCAM) and APP in neurite outgrowth using two different experimental systems: PC12E2 cells and hippocampal neurons that were isolated from wild type, APP knock-in and APP knock-out mice. PC12E2 cells or hippocampal neurons were co-cultured with NCAM-negative or NCAM-positive fibroblasts L929 cells. We found that APP promoted neurite outgrowth of PC12E2 cells and hippocampal neurons in either the presence or absence of NCAM. Secreted APP can rescue the neurite outgrowth in hippocampal neurons from APP knock-out mice. The interaction of APP and NCAM had synergic effect in promoting neurite outgrowth in both PC12E2 cells and hippocampal neurons. Our results suggested that the interaction of APP with NCAM played an important role in AD development and therefore could be a potential therapeutic target for AD treatment.

Mechanisms of ischemic stroke in patients with intracranial atherosclerosis: A high-resolution magnetic resonance imaging study.

High-resolution magnetic resonance imaging (HRMRI) has a unique ability to provide an evaluation of the intracranial artery wall. This study aimed to investigate the possible mechanisms of ischemic stroke in patients with intracranial atherosclerosis using HRMRI. HRMRI was performed on 55 patients (38 male and 17 female) with acute cerebral infarction to investigate the lumen-intruding plaque at the stenotic portion of the middle cerebral artery (MCA) and basilar artery (BA) and to attempt to identify the mechanisms of stroke. Penetrating artery disease (PAD) was diagnosed in 20 patients (36%) and large-artery atherosclerosis (LAA) was diagnosed in 35 patients, including 19 with parent artery plaques occluding a penetrating artery (POPA; 35%) and 16 with artery-to-artery embolisms (29%). Patients with PAD had a higher frequency of hypertension compared with that of the patients with LAA (80 versus 29%; P<0.001), and patients with LAA had a higher frequency of diabetes compared with that of the patients with PAD (40% versus 15%; P=0.054). Magnetic resonance angiography revealed mild to moderate stenosis in the patients with POPA, while border zone infarction and artery-to-artery embolism occurred in the majority of the patients with severe stenosis or occlusion of the MCA and BA. HRMRI has the ability to identify the mechanisms of intracranial atherosclerotic ischemic stroke through the detection of luminal plaques.

Atherosclerotic plaque pathohistology and classification with high-resolution MRI.

OBJECTIVE: A series of research works had proven that high-resolution magnetic resonance imaging (MRI) was an effective tool to identify the morphological appearance of atherosclerotic vulnerable plaque. We performed further study to compare ex vivo vascular morphology with MRI and histological examination using the specimens of carotid endarterectomy and femoral artery (FA) prosthetic reconstruction, and described the detailed histology and immunohistochemistry features of plaque. METHODS: Eight consecutive patients (five males, mean age 67.4 years) who were recruited into our study had high-grade stenosis or occlusion of carotid artery and FA (70 to 100%). Four patients accepted carotid endarterectomy and others underwent FA prosthetic reconstruction. RESULTS: The high level of accuracy was shown in classification of the plaque type. The sections of plaques detected by MRI were classified as follows: 12 (22.2%) were modified American Heart Association (AHA) type III, 11 (20.4%) were type IV-V, 26 (48.2%) were type VI and 5 (9.3%) were type VII. According to the histological observations, the overall accurate rate by MRI showed a high level accuracy of 90.7% (49/54). Immunohistochemistry of cellular components in plaque shoulder demonstrated that CD68-positive macrophages were strongly dominated along the arterial wall. Reduced expression of smooth muscle actin (SMA)-positive smooth muscle cells were detected in the fibrous cap of atheroma. CD31 stain showed the increased presence of CD31-positive neomicrovessels. CONCLUSIONS: Atherosclerosis is a systematic disease that can involve whole body vascular beds. Non-invasive high-resolution MRI will provide useful information in morphological studies of the arterial walls and classification of the plaque type.

Hemorrhage and large lipid-rich necrotic cores are independently associated with thin or ruptured fibrous caps: an in vivo 3T MRI study.

OBJECTIVE: Histological studies suggest associations between hemorrhage and large lipid-rich/necrotic cores with thin or ruptured fibrous caps in advanced atherosclerosis. We investigated these associations in carotid arteries with mild to severe stenosis by in vivo 3T MRI. METHODS AND RESULTS: Seventy-seven patients with >or=50% carotid stenosis in at least one side by duplex ultrasound underwent bilateral multi-contrast carotid MRI scans. Measurements for wall and lipid-rich/necrotic core sizes, presence of hemorrhage, and fibrous cap status (classified as intact thick, intact thin or ruptured) were recorded. Arteries with poor image quality, occlusion, or no detectable lipid-rich/necrotic core were excluded. For the 798 MRI slices included, multivariate ordinal regression analysis demonstrated larger %lipid-rich/necrotic core (odds ratio for 10% increase, 1.49; P=0.02) and presence of hemorrhage (odds ratio, 5.91; P<0.001) were independently associated with a worse (intact thin or ruptured) stage of fibrous cap status. For artery-based multivariate analysis, a larger maximum %lipid-rich/necrotic core and presence of hemorrhage independently associated with worse fibrous cap status (P<0.001, for both). No hemorrhage was detected in arteries with thick fibrous caps. CONCLUSIONS: Hemorrhage and larger %lipid-rich/necrotic core were independently associated with a thin or ruptured fibrous cap status at an early to advanced stage of carotid atherosclerosis.

Atherosclerotic carotid vulnerable plaque and subsequent stroke: a high-resolution MRI study.

BACKGROUND: High-resolution contrast-enhanced magnetic resonance imaging (CEMRI) has been proven to be an effective tool for the identification of carotid atherosclerotic vulnerable plaque, such as a large lipid core and thin fibrous cap. The aim of this study was to evaluate the relationship between carotid plaque characteristics and the types of stroke in patients who had carotid artery (CA) stenosis > or =50%. METHODS: 102 consecutive subjects (mean age 67.2 +/- 10.2 years; 73 males) who initially had ischemic stroke or asymptomatic CA stenosis from 50 to 100% diagnosed by ultrasound were included in this study. Carotid CEMRI, brain MRI and magnetic resonance angiography were performed to understand the infarct patterns and to exclude intracranial artery stenosis. The modified American Heart Association (AHA) plaque classification was used in our study. RESULTS: Our study demonstrated that 45 patients had CA stroke, and 55 patients had lacunar and asymptomatic lesions. The majority of patients had AHA classification type IV-V and VI which presented as vulnerable plaques. Of 63 patients with mild to moderate stenosis (< or =70%), 44 (69.8%) had type IV-V vulnerable plaques, which was significantly higher than those of patients with severe stenosis (>70%; p < 0.001). In CA stroke, the number of patients with a thin or ruptured fibrous cap was twice that of those with a thick and intact fibrous cap. CONCLUSIONS: CEMRI may have important applications in clinical risk evaluations in CA atherosclerosis. Physicians ought to recognize that different types of stroke should be identified by brain MRI detection before invasive therapies.

Silent cerebral microbleeds on susceptibility-weighted imaging of patients with ischemic stroke and leukoaraiosis.

OBJECTIVE: Cerebral microbleeds (CMBs) are an increasingly recognized in patients with cerebrovascular disease who undergo the new MRI techniques. Susceptibility-weighted MRI is sensitive to detect silent microbleeds which are associated with microangiopathy from atherosclerosis, amyloid angiopathy or asymptomatic elderly individuals. CMBs are intracerebral old hemosiderin deposits in the perivascular space, and the clinical significance of such 'microbleeds' remains controversy. We investigated the incidence of microbleeds among different ischemic stroke subtypes and the severity of leukoaraiosis. METHODS: In this study, we collected 137 patients (73.5 +/- 9.1 years old, 84 men and 53 women) who were divided into five groups: atherothrombotic infarction (34 patients), cardioembolic infarction (24 patients), lacunar infarction (35 patients), other determined or undetermined infarction (21 patients) and control (23 patients), in which 52 had primary stroke and 62 had recurrent stroke. Microbleeds were counted and leukoaraiosis was graded using susceptibility-weighted, T1-, T2- and FLAIR MRI with a 3.0 T system. RESULTS: Microbleeds were high in lacunar infarction (25.7%) and atherothrombotic infarction patients (20.6%). Microbleeds were low in patients with cardioembolic infarction (4.2%). Both microbleeds (> or =grade 2) and leukoaraiosis in severity (> or =grade 2) were higher in the recurrent stroke group (14.5 and 48.4%) than those in the primary stroke group (3.8 and 7.7%). Leukoaraiosis (r=0.803, p<0.05) and recurrent stroke (r=0.708, p<0.05) were significantly associated with microbleeds. CONCLUSIONS: Asymptomatic CMBs are observed with a markedly higher frequency in recurrent stroke, and are closely associated with the severity of leukoaraiosis.