259 research outputs found

    Elastic scattering and total reaction cross sections of 6^{6}Li studied with a microscopic continuum discretized coupled channels model

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    We present a systematic study of 6^{6}Li elastic scattering and total reaction cross sections at incident energies around the Coulomb barrier within the continuum discretized coupled-channels (CDCC) framework, where 6^{6}Li is treated in an Ξ±\alpha+dd two-body model. Collisions with 27^{27}Al, 64^{64}Zn, 138^{138}Ba and 208^{208}Pa are analyzed. The microscopic optical potentials (MOP) based on Skyrme nucleon-nucleon interaction for Ξ±\alpha and dd are adopted in CDCC calculations and satisfactory agreement with the experimental data is obtained without any adjustment on MOPs. For comparison, the Ξ±\alpha and dd global phenomenological optical potentials (GOP) are also used in CDCC analysis and a reduction no less than 50%\% on the surface imaginary part of deuteron GOP is required for describing the data. In all cases, the 6^6Li breakup effect is significant and provides repulsive correction to the folding model potential. The reduction on the GOP of deuteron reveals a strong suppression of the reaction probability of deuteron as a component of 6^{6}Li as compared with that of a free deuteron. A further investigation is made by taking the dd breakup process into account equivalently within the dynamic polarization potential approach and it shows that dd behaves like a tightly bound nucleus in 6^{6}Li induced reactions. We also compare the CDCC results with those calculated with a 6^6Li GOP and it shows that CDCC calculations provide a better reproduction for the elastic scattering angular distributions in the sub-barrier energy region and the total reaction cross sections at energies around the Coulomb barrier.Comment: 10 pages, 12 figure

    Transient and permanent resolution of ischemic lesions on diffusion-weighted imaging after brief periods of focal ischemia in rats : correlation with histopathology

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    BACKGROUND AND PURPOSE: The early ischemic lesions demonstrated by diffusion-weighted imaging (DWI) are potentially reversible. The purposes of this study were to determine whether resolution of initial DWI lesions is transient or permanent after different brief periods of focal brain ischemia and to evaluate histological outcomes. METHODS: Sixteen rats were subjected to 10 minutes (n=7) or 30 minutes (n=7) of temporary middle cerebral artery occlusion or sham operation (n=2). DWI, perfusion-weighted imaging (PWI), and T(2)-weighted imaging (T(2)WI) were performed during occlusion; immediately after reperfusion; and at 0.5, 1.0, 1.5, 12, 24, 48, and 72 hours after reperfusion. After the last MRI study, the brains were fixed, sectioned, stained with hematoxylin and eosin, and evaluated for neuronal necrosis. RESULTS: No MRI or histological abnormalities were observed in the sham-operated rats. In both the 10-minute and 30-minute groups, the perfusion deficits and DWI hyperintensities that occurred during occlusion disappeared shortly after reperfusion. The DWI, PWI, and T(2)WI results remained normal thereafter in the 10-minute group, whereas secondary DWI hyperintensity and T(2)WI abnormalities developed at the 12-hour observation point in the 30-minute group. Histological examinations demonstrated neuronal necrosis in both groups, but the number of necrotic neurons was significantly higher in the 30-minute group (95+/-4%) than in the 10-minute group (17+/-10%, P\u3c0.0001). CONCLUSIONS: Transient or permanent resolution of initial DWI lesions depends on the duration of ischemia. Transient resolution of DWI lesions is associated with widespread neuronal necrosis; moreover, permanent resolution of DWI lesions does not necessarily indicate complete salvage of brain tissue from ischemic injury

    SN 2022vqz: A Peculiar SN 2002es-like Type Ia Supernova with Prominent Early Excess Emission

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    We present extensive photometric and spectroscopic observations of a peculiar type Ia supernova (SN Ia) 2022vqz. It shares many similarities with the SN 2002es-like SNe Ia, such as low luminosity (i.e., MB,max=βˆ’18.11Β±0.16M_{B,\rm max}=-18.11\pm0.16 mag) and moderate post-peak decline rate (i.e., Ξ”m15,B=1.33Β±0.11\Delta m_{15,B}=1.33\pm0.11 mag). The nickel mass synthesized in the explosion is estimated as 0.20Β±0.04Β MβŠ™0.20\pm0.04~{\rm M}_\odot from the bolometric light curve, which is obviously lower than normal SNe Ia. SN 2022vqz is also characterized by a slow expanding ejecta, with Si II velocities persisting around 7000 km sβˆ’1^{-1} since 16 days before the peak, which is unique among all known SNe Ia. While all these properties imply a less energetic thermonuclear explosion that should leave considerable amount of unburnt materials, however, absent signature of unburnt carbon in the spectra of SN 2022vqz is puzzling. A prominent early peak is clearly detected in the cc- and oo-band light curves of ATLAS and in the grgr-band data of ZTF within days after the explosion. Possible mechanisms for the early peak are discussed, including sub-Chandrasekhar mass double detonation model and interaction of SN ejecta with circumstellar material (CSM). We found both models face some difficulties in replicating all aspects of the observed data. As an alternative, we propose a hybrid CONe white dwarf as progenitor of SN 2022vqz which can simultaneously reconcile the tension between low ejecta velocity and absence of carbon. We further discuss the diversity of 02es-like objects and possible origins of different scenarios.Comment: 24 pages, 12 figures, submitted to MNRA

    Transmission Pattern of Drug-Resistant Tuberculosis and Its Implication for Tuberculosis Control in Eastern Rural China

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    OBJECTIVE: Transmission patterns of drug-resistant Mycobacterium tuberculosis (MTB) may be influenced by differences in socio-demographics, local tuberculosis (TB) endemicity and efficaciousness of TB control programs. This study aimed to investigate the impact of DOTS on the transmission of drug-resistant TB in eastern rural China. METHODS: We conducted a cross-sectional study of all patients diagnosed with drug-resistant TB over a one-year period in two rural Chinese counties with varying lengths of DOTS implementation. Counties included Deqing, with over 11 years' DOTS implementation and Guanyun, where DOTS was introduced 1 year prior to start of this study. We combined demographic, clinical and epidemiologic information with IS6110-based restricted fragment length polymorphism (RFLP) and Spoligotyping analysis of MTB isolates. In addition, we conducted DNA sequencing of resistance determining regions to first-line anti-tuberculosis agents. RESULTS: Of the 223 drug-resistant isolates, 73(32.7%) isolates were identified with clustered IS6110RFLP patterns. The clustering proportion among total drug-resistant TB was higher in Guanyun than Deqing (26/101.vs.47/122; p,0.04), but not significantly different among the 53 multidrug-resistant isolates (10/18.vs.24/35; p,0.35). Patients with cavitary had increased risk of clustering in both counties. In Guanyun, patients with positive smear test or previous treatment history had a higher clustering proportion. Beijing genotype and isolates resistant to isoniazid and/or rifampicin were more likely to be clustered. Of the 73 patients with clustered drug-resistant isolates, 71.2% lived in the same or neighboring villages. Epidemiological link (household and social contact) was confirmed in 12.3% of the clustered isolates. CONCLUSION: Transmission of drug-resistant TB in eastern rural China is characterized by small clusters and limited geographic spread. Our observations highlight the need for supplementing DOTS with additional strategies, including active case finding at the village level, effective treatment for patients with cavities and drug susceptibility testing for patients at increased risk for drug-resistance

    Extensive transmission of isoniazid resistant M. tuberculosis and its association with increased multidrug-resistant TB in two rural counties of eastern China: A molecular epidemiological study

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    <p>Abstract</p> <p>Background</p> <p>The aim of this study was to investigate the molecular characteristics of isoniazid resistant <it>Mycobacterium tuberculosis </it>(MTB), as well as its contribution to the dissemination of multi-drug resistant TB (MDR-TB) in rural areas of eastern China.</p> <p>Methods</p> <p>A population-based epidemiological study was conducted in two rural counties of eastern China from 2004 to 2005. In total, 131 isoniazid resistant MTB isolates were molecularly characterized by DNA sequencing and genotyped by IS<it>6110 </it>restriction fragment length polymorphism (RFLP) and spoligotyping.</p> <p>Results</p> <p>The <it>katG</it>315Thr mutation was observed in 74 of 131 isoniazid resistant isolates and more likely to be MDR-TB (48.6%) and have mutations in <it>rpoB </it>gene (47.3%). Spoligotyping identified 80.2% of isoniazid resistant MTB isolates as belonging to the Beijing family. Cluster analysis by genotyping based on IS<it>6110 </it>RFLP, showed that 48.1% isoniazid resistant isolates were grouped into 26 clusters and <it>katG</it>315Thr mutants had a significantly higher clustering proportion compared to those with <it>katG </it>wild type (73%.vs.18%; OR, 12.70; 95%CI, 6.357-14.80). Thirty-one of the 53 MDR-TB isolates were observed in 19 clusters. Of these clusters, isoniazid resistance in MDR-TB isolates was all due to the <it>katG</it>315Thr mutation; 18 clusters also contained mono-isoniazid resistant and other isoniazid resistant isolates.</p> <p>Conclusions</p> <p>These results highlighted that isoniazid resistant MTB especially with <it>katG</it>315Thr is likely to be clustered in a community, develop extra resistance to rifampicin and become MDR-TB in Chinese rural settings.</p

    Effect of Abuse History on Pain Reports and Brain Responses to Aversive Visceral Stimulation: An fMRI Study

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    Abuse history is common in irritable bowel syndrome (IBS) and is associated with greater pain reporting, psychologic distress, and poorer health outcome. These effects may be mediated by enhanced responses to aversive visceral stimuli. We investigated the effects of IBS and abuse history on pain reporting and brain activation in response to rectal distentions. Ten female patients with IBS and 10 controls were included. Half of patients in each group reported a history of abuse. Brain functional magnetic resonance imaging (fMRI) images and pain ratings were obtained during rectal distentions. Statistical parametric mapping identified activation in subregions of the dorsal cingulate cortex and covariation with rated pain. (1) Distention-elicited pain correlated with anxiety and activation of the posterior (PCC) and middle (MCC) dorsal cingulate subregions. (2) Subjects with a history of abuse showed greater activation in the left MCC ( = .022; t = 5.61) and PCC ( = .033; t = 5.00) than subjects without abuse. (3) Those with IBS and abuse reported greater pain than all others ( = .004), had more activity in the left MCC ( = .021; t = 5.29) and PCC ( = .049; t = 4.81), and had less activity in the left supragenual anterior cingulate (sACC) ( = .01; t = 4.86). Pain ratings during rectal distention are associated with activation of dorsal cingulate regions implicated in homeostatic afferent processing, and prior abuse enhances this activation. Patients with IBS and abuse report more pain, greater MCC/PCC activation, and reduced activity of a region implicated in pain inhibition and arousal (sACC). These findings suggest a possible explanation for the clinical observation of greater pain reporting and poorer outcome in IBS patients with a history of abuse

    Conjugation of Functionalized SPIONs with Transferrin for Targeting and Imaging Brain Glial Tumors in Rat Model

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    Currently, effective and specific diagnostic imaging of brain glioma is a major challenge. Nanomedicine plays an essential role by delivering the contrast agent in a targeted manner to specific tumor cells, leading to improvement in accurate diagnosis by good visualization and specific demonstration of tumor cells. This study investigated the preparation and characterization of a targeted MR contrast agent, transferrin-conjugated superparamagnetic iron oxide nanoparticles (Tf-SPIONs), for brain glioma detection. MR imaging showed the obvious contrast change of brain glioma before and after administration of Tf-SPIONs in C6 glioma rat model in vivo on T2 weighted imaging. Significant contrast enhancement of brain glioma could still be clearly seen even 48 h post injection, due to the retention of Tf-SPIONs in cytoplasm of tumor cells which was proved by Prussian blue staining. Thus, these results suggest that Tf-SPIONs could be a potential targeting MR contrast agent for the brain glioma

    Is Human Cytomegalovirus Infection Associated with Hypertension? The United States National Health and Nutrition Examination Survey 1999–2002

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    PURPOSE: Recent studies have implicated the human cytomegalovirus (HCMV) as a possible pathogen for causing hypertension. We aimed to study the association between HCMV infection and hypertension in the United States National Health and Nutrition Examination Survey (NHANES). METHODS: We analyzed data on 2979 men and 3324 women in the NHANES 1999-2002. We included participants aged 16-49 years who had valid data on HCMV infection and hypertension. RESULTS: Of the participants, 54.7% had serologic evidence of HCMV infection and 17.5% had hypertension. There were ethnic differences in the prevalence of HCMV infection (P<0.001) and hypertension (P<0.001). The prevalence of both increased with age (P<0.001). Before adjustment, HCMV seropositivity was significantly associated with hypertension in women (OR = 1.63, 95% CI = 1.25-2.13, P = 0.001) but not in men. After adjustment for race/ethnicity, the association between HCMV seropositivity and hypertension in women remained significant (OR = 1.55, 95% CI = 1.20-2.02, P = 0.002). Further adjustment for body mass index, diabetes status and hypercholesterolemia attenuated the association (OR = 1.44, 95% CI = 1.10-1.90, P = 0.010). However, after adjusting for age, the association was no longer significant (OR = 1.24, 95% CI = 0.91-1.67, P = 0.162). CONCLUSIONS: In this nationally representative population-based survey, HCMV seropositivity is associated with hypertension in women in the NHANES population. This association is largely explained by the association of hypertension with age and the increase in past exposure to HCMV with age.published_or_final_versio
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