668 research outputs found
Immunotherapy for neurodegeneration?
Alzheimer's disease (AD), Parkinson's disease (PD), and prion diseases such as Creutzfeldt-Jakob disease attack different parts of the central nervous system (CNS) and elicit distinct symptoms, yet they share many biochemical and neuropathological features. These include the formation of protein aggregates in the affected brain regions and progressive activation of non-neuronal cells in the brain that play crucial roles in immune responses. The activation of immune cells in the CNS (“neuroinflammation”) is prominent in these diseases. However, it remains unclear whether boosting or suppressing the immune system, in the brain or in the periphery, may attenuate neurodegeneration. In the case of extraneural prion infections, genetic or pharmacological ablation of components of the immune system, such as B cells and complement, can prevent disease (1). However, immunotherapies, which have been successful in treating certain types of cancer, have yet to reverse neurodegeneration in any patients. Therefore, the therapeutic promise of this approach remains debatable
Changes in Stable Fraction of Soil Organic Carbon and Microbial Structure in Response of Grazing Intensity
Carbon sequestration is one of the most important ecological function of the grassland. Soils contain more carbon than in vegetation in the form of soil organic matter (SOM). But grassland soils are vulnerable to disturbances caused by human activities. Grazing may result in various disturbances to both soil and vegetation under different grazing intensities (Bai et al., 2012). Grazing led to the shifts in amount and composition of soil organic matter. In previous studies, the chemical methods were used to separate soil into the different pools according to the stability of SOM (Carvalho Leite et al., 2004), but they cannot be convictive for their chemical destruction upon the SOM structure. In this study, we use more credible fractionating method to separate stable part of the SOM based on the dry sieving and winnowing (Kirkby et al., 2011).
Stable carbon fraction has two origins: microbial debris and recalcitrant plant materials (Lehmann et al., 2007). Evidences have showed that soil microbial community alters metabolic rates by changing its composition adjust to stoichiometry of substrates. We hypothesize that carbon content stable fraction SOM in the surface soils would decline as the intensity increasing, but the stoichiometry of carbon and nutrients (N and P) would remain constant. We also predict that the relative importance in carbon sequestration of microbial groups would change due to the soil environmental alteration. The objectives of the study is to evaluate the effects of grazing intensity (GI) on carbon in more stabilized SOM and on soil microbial community structure in steppe
Morpholpgy Dependence of Hybrid Nanofibers Incoorporated with Nanoparticles of Electrospinning and Post-treatment Conditions
Master'sMASTER OF ENGINEERIN
On the Role of Exotic Hero of Archery Target Type in Kūshnāma Played in Reconstructing Iranian National Identity
In the process of Islamization after the 7th century, Iranian native ancestral conception and historical identity were severely eroded and interfered by foreign ideas. Under the background of the boom of New Persian language and literature, some Iranian literati assumed the mission of being the bearers of cultural memory. Collected and compiled on the basis of the ancient Iranian oral and written legends, certain Iranian national epics composed from the 10th to the 12th century show a significant influence on the survival of Iranian cultural tradition. Among the epics, Kūshnāma is particularly remarkable for its creation of an alien hero. After close scrutiny of the text, we can find that this so-called “Story of the King of China” integrates the fragments of the ancient Iranians’ collective cultural memory – the bygone military conflicts between the alien enemy chieftains and the Iranian people. The hero, acting as a typical character of the “archery target type”, is derived from multiple prototypes, which include the Kushite kings, the legendary Mesopotamian Semitic kings represented by Nimrud, as well as the kings of the Kushan Empire. Kūshnāma, therefore, by shaping an exotic hero of the archery target type with multiple identities of foreign enemies, draws the brilliant achievements of legendary Iranian kings and heroes together. Meanwhile, it contributes to establishing a comprehensive frame of reference for the rejuvenation of Iranian national memory. In other words, through recognizing the self by concretizing the other, the epic plays an important role in refashioning Iranian national identity in the Islamic era
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Isoprene Photooxidation via the Hydroperoxyl Pathway
Photooxidation of isoprene has a large influence on the oxidation capacity of the atmosphere and is a significant source of secondary organic material (SOM) of atmospheric particles. A quantitative understanding of isoprene photooxidation mechanism, in particular in the clean atmosphere, is important but challenging. This thesis presents laboratory and field studies of isoprene photooxidation via the hydroperoxyl (HO2) pathway, believed to be the most important reaction pathway of isoprene-derived peroxy radicals under clean conditions, by using a switchable-reagent-ion (NO+; H3O+) time-of-flight mass spectrometer (SRI-TOF-MS).
Isoprene photooxidation via the HO2 pathway was investigated in a continuous-flow chamber. Production yields of methyl vinyl ketone (MVK) and methacrolein (MACR) pathway were determined as (3.8 ± 1.3)% and (2.5 ± 0.9)%, respectively, at <2% RH at 25 oC. Production of MVK and MACR via the HO2 pathway implies concomitant production of hydroxyl ((6.3± 2.1)%) and hydroperoxyl ((6.3± 2.1)%) radicals.
The experiments also revealed an unexpected instrument bias that isoprene-derived hydroperoxides (ISOPOOH), the major isoprene oxidation products via the HO2 pathway, were detected as the same product ions as the MVK and MACR. This finding implies that scientific conclusions based on previous ambient measurements of MVK and MACR under clean conditions using similar techniques need to be revisited. As a follow-up study, preliminary analysis of the ambient measurements in the Amazon Basin showed that ISOPOOH isomers contributed to (36±15)% of the total concentration of MVK, MACR, and ISOPOOH isomers under clean conditions. The value is useful for re-evaluation of previous measurements and also defines range of possible anthropogenic influence on isoprene chemistry in the region.
SOM production from isoprene photooxidation via the HO2 pathway was also investigated. Isoprene photooxidation was separated from SOM production by using two continuous-flow reactors connected in series and operated at steady state. Relative importance of various intermediates was directly compared from the drop of their gas-phase signals. Isoprene epoxydiols (IEPOX) had a much larger contribution to SOM production than other previously suggested isoprene SOM precursor, ISOPOOH isomers and isoprene, for a wide range of aciddity
The IEPOX contribution to isoprene SOM production was further quantified. IEPOX isomers lost from the gas phase accounted for (46 ±11)% of the produced SOM mass concentration. The IEPOX isomers comprised (59±21)% (molecular count) of the loss of monitored gas-phase species. The implication is that for the investigated reaction conditions IEPOX pathway accounted for half of the SOM mass concentration
Differences in Species Composition of the Soil Seed Banks among Degraded Patches in an Agro-Pastoral Transition Zone in Inner Mongolian Steppe
Degraded grasslands were distributed in patches characterized by fringed sagebrush (Artemisia frigida), narrowleaf stellera (Stellera chamaejasme), shining speargrass (Achnatherum splendens), or white swordflag (Iris lactea) at an agro-pastoral transition zone of the south Inner Mongolian steppe, which have been retrogressive from a Leymus chinensis steppe. A control patch (undegraded) was located close to the four degraded patches. We investigated the size, composition, species richness of soil seed banks, and its relation to the aboveground vegetation. The density of soil seed banks was highest in the white swordflag patch, intermediate in the shining speargrass and undegraded patches and lowest in the fringed sagebrush and narrowleaf stellera patches. The percentage of the persistent seed bank in the undegraded patch was higher than those in the four degraded patches. Similarities between the soil seed bank of the undegraded patch and degraded patches and between soil seed banks and standing vegetation of the undegraded patch were all low. The potential for in situ regeneration of the established vegetation of the undegraded patch from the soil seed bank is low in all of these four patches. We can assume that restoration of these habitats can not rely on seed banks alone
A novel method for computing the Hilbert transform with Haar multiresolution approximation
AbstractIn this paper, an algorithm for computing the Hilbert transform based on the Haar multiresolution approximation is proposed and the L2-error is estimated. Experimental results show that it outperforms the library function ‘hilbert’ in Matlab (The MathWorks, Inc. 1994–2007). Finally it is applied to compute the instantaneous phase of signals approximately and is compared with three existing methods
A New Approach for the Discovery of Antibiotics by Targeting Non-Multiplying Bacteria: A Novel Topical Antibiotic for Staphylococcal Infections
In a clinical infection, multiplying and non-multiplying bacteria co-exist. Antibiotics kill multiplying bacteria, but they are very inefficient at killing non-multipliers which leads to slow or partial death of the total target population of microbes in an infected tissue. This prolongs the duration of therapy, increases the emergence of resistance and so contributes to the short life span of antibiotics after they reach the market. Targeting non-multiplying bacteria from the onset of an antibiotic development program is a new concept. This paper describes the proof of principle for this concept, which has resulted in the development of the first antibiotic using this approach. The antibiotic, called HT61, is a small quinolone-derived compound with a molecular mass of about 400 Daltons, and is active against non-multiplying bacteria, including methicillin sensitive and resistant, as well as Panton-Valentine leukocidin-carrying Staphylococcus aureus. It also kills mupirocin resistant MRSA. The mechanism of action of the drug is depolarisation of the cell membrane and destruction of the cell wall. The speed of kill is within two hours. In comparison to the conventional antibiotics, HT61 kills non-multiplying cells more effectively, 6 logs versus less than one log for major marketed antibiotics. HT61 kills methicillin sensitive and resistant S. aureus in the murine skin bacterial colonization and infection models. No resistant phenotype was produced during 50 serial cultures over a one year period. The antibiotic caused no adverse affects after application to the skin of minipigs. Targeting non-multiplying bacteria using this method should be able to yield many new classes of antibiotic. These antibiotics may be able to reduce the rate of emergence of resistance, shorten the duration of therapy, and reduce relapse rates
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