Phase Space Dynamics of a Plasma Wakefield Dechirper for Energy Spread Reduction.

Plasma-based accelerators have made impressive progress in recent years. However, the beam energy spread obtained in these accelerators is still at the ∼1% level, nearly one order of magnitude larger than what is needed for challenging applications like coherent light sources or colliders. In plasma accelerators, the beam energy spread is mainly dominated by its energy chirp (longitudinally correlated energy spread). Here we demonstrate that when an initially chirped electron beam from a linac with a proper current profile is sent through a low-density plasma structure, the self-wake of the beam can significantly reduce its energy chirp and the overall energy spread. The resolution-limited energy spectrum measurements show at least a threefold reduction of the beam energy spread from 1.28% to 0.41% FWHM with a dechirping strength of ∼1 (MV/m)/(mm pC). Refined time-resolved phase space measurements, combined with high-fidelity three-dimensional particle-in-cell simulations, further indicate the real energy spread after the dechirper is only about 0.13% (FWHM), a factor of 10 reduction of the initial energy spread.

[Effect of cigarette smoke exposure on the expression of CCR7 and levels of Th1/Th2 cytokines in asthmatic rats].

Objective: To investigate the effect of cigarette smoke exposure on the expression of CC Chemokine receptor 7 (CCR7) and levels of Th1/Th2 cytokines in asthmatic rats. Methods: Forty Wistar rats were randomly divided into four groups: control group, asthma group, smoke exposure group, asthma-smoke exposure group. The asthma group were sensitized with ovalbumin (OVA) and Aluminum hydroxide at day 1, 8 and challenged with OVA at day 15 by atomization for 8 weeks.While control group was sensitized and challenged with normal saline instead of OVA.The smoke exposure group was sensitized and challenged with normal saline instead of OVA followed passive smoking for 8 weeks. The asthma-smoke exposure group was challenged with OVA followed passive smoking. The pathological changes of different groups were observed by HE-staining. CCR7 was semiquantitatively analyzed in lungs by immunohistochemistry.The concentration of CC chemokine ligand (CCL)19, CCL21, interferon (IFN)-γ and interleukin (IL)-4 in peripheral blood and CCL19 and CCL21 in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent (ELESA) assay. Results: In asthma group, smoke exposure group and asthma-smoke exposure group, the various degrees of inflammatory reaction appeared in lung tissue and the asthma-smoke exposure group was with the most significant reaction. In the lung tissues of the rats from asthma group, smoke exposure group and asthma-smoke exposure group, the average optical density (AOD) of CCR7 were significantly higher than those in control group (0.350±0.023, 0.252±0.022, 0.400±0.029 vs 0.180±0.020, all P<0.01). The AOD of CCR7 of asthma-smoke exposure group was much higher than both that in asthma group and in smoke exposure group (both P<0.01). In asthma group, smoke exposure group and asthma-smoke exposure group, the concentrations of both CCL19 and CCL21 in peripheral blood and BALF were significantly higher than that in control group (all P<0.01). The concentrations of both CCL19 and CCL21 in peripheral blood and BALF of asthma-smoke exposure group were significantly higher than the results in asthma group and in smoke exposure group (all P<0.01). The concentrations of IFN-γ in peripheral blood of asthma group and asthma-smoke exposure group were lower than those in control group [(33±3), (17±3) vs (70±4) pg/ml], but asthma-smoke exposure group was much lower than the results in asthma group (all P<0.01). The concentration of IFN-γ in peripheral blood of smoke exposure group[(100±5)pg/ml]was higher than that in control group and asthma-smoke exposure group (both P<0.01). In asthma group, smoke exposure group, asthma-smoke exposure group, the concentrations of IL-4 in peripheral blood were significantly higher than those in control group [(54±4), (42±4), (76±4) vs (30±4) pg/ml, all P<0.01]. The concentrations of IL-4 in peripheral blood of asthma-smoke exposure group was significantly higher than those in asthma group and in smoke exposure group (both P<0.01). Conclusion: Cigarette smoke could enhance the expression of CCR7 and its ligand, and it can also result in exacerbations of asthma by reducing the expression level of IFN-γ (the representative of Th1 cytokine) and increasing the expression level of IL-4 (the representative of Th2 cytokine).

Phase-space dynamics of ionization injection in plasma-based accelerators.

The evolution of beam phase space in ionization injection into plasma wakefields is studied using theory and particle-in-cell simulations. The injection process involves both longitudinal and transverse phase mixing, leading initially to a rapid emittance growth followed by oscillation, decay, and a slow growth to saturation. An analytic theory for this evolution is presented and verified through particle-in-cell simulations. This theory includes the effects of injection distance (time), acceleration distance, wakefield structure, and nonlinear space charge forces, and it also shows how ultralow emittance beams can be produced using ionization injection methods.

Generating high-brightness electron beams via ionization injection by transverse colliding lasers in a plasma-wakefield accelerator.

The production of ultrabright electron bunches using ionization injection triggered by two transversely colliding laser pulses inside a beam-driven plasma wake is examined via three-dimensional particle-in-cell simulations. The relatively low intensity lasers are polarized along the wake axis and overlap with the wake for a very short time. The result is that the residual momentum of the ionized electrons in the transverse plane of the wake is reduced, and the injection is localized along the propagation axis of the wake. This minimizes both the initial thermal emittance and the emittance growth due to transverse phase mixing. Simulations show that ultrashort (~8 fs) high-current (0.4 kA) electron bunches with a normalized emittance of 8.5 and 6 nm in the two planes, respectively, and a brightness of 1.7×10(19) A rad(-2) m(-2) can be obtained for realistic parameters.

Sirt7 protects chondrocytes degeneration in osteoarthritis via autophagy activation.

OBJECTIVE: Osteoarthritis (OA) is associated with decreased autophagy activity and imbalance of cell homeostasis in chondrocytes (CHs). Sirtuin 7 (Sirt7) is claimed to have the ability to activate the autophagy response. The aim of this study was to explore the function of Sirt7 in the development of OA involving autophagy by culturing human chondrocytes (CHs). PATIENTS AND METHODS: We collected knee joint cartilage from patients undergoing traumatic amputation and arthroscopic knee replacement. Protein and mRNA levels of collagen II, Sirt7, ULK1, Lc3, and Beclin1 were analyzed by Western blot and RT-PCR. CHs were isolated from the traumatic cartilage as a control group, and IL-1ß was used to induce CHs degeneration. The expression of Sirt7 gene was silenced by siRNA and upregulated by recombinant human Sirt7 protein (rh-Sirt7). An autophagy activator Tat-beclin 1 (Tat) was used to activate autophagy in cultural CHs. Expression of collagen II, Sirt7, ULK1, Lc3, and Beclin1 was determined by immunofluorescence, Western blot, and RT-PCR, respectively. RESULTS: The protein and mRNA levels of Collagen II, Sirt7, ULK1, Lc3-II, and Beclin1 expressions were decreased in OA cartilage compared with those in healthy cartilage. IL-1ß degenerated the CHs resulting in a reduction of collagen II, which also downregulated Sirt7, ULK1, Lc3-II, and Beclin1. Sirt7 deficiency accelerated the catabolism of collagen II and weakened the expression of ULK1, Lc3-II, and Beclin1. On the contrary, exogenous rh-Sirt7 played a positive role in these gene expressions. Finally, Tat alleviated the CHs degeneration by upregulating collagen II and activating ULK1, Lc3-II, and Beclin1, but incapable to mediate Sirt7 expression. CONCLUSIONS: Overall, these findings suggested that Sirt7 was suppressed in the degenerated cartilage. Sirt7 deficiency does harm to the autophagy level, affecting CHs metabolism, while the upregulation of Sirt7 activated autophagy and protected CHs degeneration. An appropriate increase in autophagy can protect CHs but has no effect on Sirt7 expression.

Function and molecular basis of action of vasopressin 4-8 and its analogues in rat brain.

VP 4-8 as a highly potent behavioral-active metabolite of arginine-vasopressin (VP) has been studied in detail at four levels, i.e. ligand level, membrane binding level, intracellular level and nuclear level. The purpose of this chapter is to review and discuss the main results obtained from our recent pharmacological and biochemical investigations which are described as follows: 1, structure-function relationship of VP 4-8 and its analogs; 2, some characters of VP 4-8-specific binding, the distribution of the binding sites in the rat brain and the consequent effect on long-term potentiation of synaptic transmission; 3, a putative receptor-mediated signaling pathway involving second messenger IP3, immediately-early gene c-fos transcription and protein kinase PKC, CaMKII and MAPK; 4, peptide-induced enhancement of some crucial functional proteins such as calmodulin, nerve growth factor (NGF) and brain-derived nerve growth factor (BDNF). The physiological significance of the events following VP 4-8 administration and particularly, its possible role in learning and memory processes are discussed.

Potentiation of synaptic transmission by neuropeptide AVP4-8 (ZNC(C)PR) in rat hippocampal slices.

The effect of AVP4-8 on synaptic transmission in rat hippocampal slices was studied using both extracellular and intracellular recording. AVP4-8 induced a long-lasting potentiation effect on the evoked EPSP and enhanced LTP in pyramidal neurones. The lowest effective concentration of AVP4-8 was 1 x 10(-12) M, three to four orders of magnitude lower than that of AVP. These findings support the concept that AVP4-8 is a new memory-enhancing peptide and should be written as ZNC(C)PR. The results show that the potentiation effect of ZNC(C)PR is mainly due to a presynaptic mechanism of action.

Cysteinyl methyl ester of AVP(4-8), a potent agonist on the maintenance of passive avoidance in rats.

A series of short AVP analogs with D- or L-arginine forming the C-terminal was synthesized, and their peripheral effects, i.e., vasoconstrictor and antidiuretic activities, and behavioral effects in enhancing retention in passive avoidance in rats were evaluated. We found that: 1) AVP(4-8) and its cysteinyl methyl ester were more potent in the behavioral response than its D-Arg homologs; 2) the methyl ester derivative was the most effective analog in this behavioral test among the peptides we synthesized, with a potency 40 times as high as AVP; 3) neither the D- nor the L-Arg short derivatives of AVP showed any peripheral effects up to a dose thousands of times greater than AVP. The results support the contention that arginine in the short analogs plays an important role in their behavioral response associated with a relatively steady peptide conformation.

Facilitation of AVP(4-8) on gene expression of BDNF and NGF in rat brain.

In situ hybridization and Northern blot assay were used to evaluate the effects of exogenous AVP(4-8) on the transcription of mRNAs for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT-3) in the adult rat brain. NGF and BDNF expression was found to be significantly enhanced by AVP(4-8) administration in the cerebral cortex and hippocampus, but NT-3 expression was not changed. In the same conditions, behavior-active arginine-vasopressin (AVP) showed a small effect and its behavior-inactive homologue, oxytocin did not. Our results suggest that selective regulation of neurotrophin gene expression by the peptides may be responsible for its memory-enhancing function.

Enhancement of NGF gene expression in rat brain by the memory-enhancing peptide AVP(4-8).

Northern blot analysis of nerve growth factor (NGF) was used to evaluate the effect of exogenous AVP(4-8) on the transcription of NGF gene in rat brain. NGF expression was found to be significantly enhanced by exogenous AVP(4-8) in the hippocampus as well as in the cerebral cortex in a time period of 12 h. This effect was inhibited by an antagonist to AVP(4-8). In addition, gel mobility shift assay was also used to observe the in vitro expression of c-fos gene in rat hippocampal slices. Our results suggest that NGF gene is one of the target genes responsible for memory-enhancing responses induced by AVP(4-8) and that the enhancement of NGF gene expression may share the signaling pathway mediated by AVP(4-8) receptor and c-fos gene expression.

Characterization of binding sites of a memory-enhancing peptide AVP(4-8) in rat cortical synaptosomal membranes.

The pentapeptide pGlu-Asn-Cyt-Pro-Arg [AVP(4-8), termed ZNC(C)PR in this article] has been found as a metabolite of arginine-vasopressin (AVP) in rat brain and has been shown to have potent memory-enhancing activity and to yield a series of biochemical events in brain tissues. [35S]ZNC(C)PR was chemically synthesized with high specific activity (232 Ci/mmol), and specific binding sites for ZNC(C)PR were located in synaptosomal membrane preparations of rat brain. We identified a specific binding site for ZNC(C)PR with a Kd of 3.12 nM and Bmax of 31 fmol/mg protein in anterior cortical synaptosomal membranes in the presence of 5 mM Ni2+. A comparison of synthetic analogues of ZNC(C)PR competing with [35S]ZNC(C)PR for binding to anterior cortical receptor are presented. ZDC(C)PR, a 2-aspartyl substitute of the 2-asparaginyl residue in ZNC(C)PR, had the most potent competition, but AVP did not show significant ability to compete for the receptor with ZNC(C)PR.

Neonatal administrations of a vasopressin analog (DDAVP) and hypertonic saline enhance learning behavior in rats.

Groups of newborn Wistar rats received daily 1-desamino-8-D-arginine-vasopressin (DDAVP), oxytocin (OXT), hypertonic saline or normal saline for 14 days from day 1 to day 14 of life. One or three months later they were trained in a maze for brightness discrimination (BD). A group of untreated adult male rats received posttrial DDAVP or normal saline for brightness discrimination. Subsequently all the retentions of BD were tested after one month. We found that the neonatal treatments with both DDAVP and hypertonic saline facilitated acquisition and subsequent maintenance of brightness discrimination in immature and mature rats, and also that posttreatment with DDAVP enhanced retention of BD in adult rats. Oxytocin and normal saline had no effect on these parameters. The results are interpreted as showing that endogenous AVP and its synthetic analog enhance the development and adult function of central neural substrates involved in learning behaviors.

Prevalence of growth hormone deficiency of children in Beijing.

103,753 (male 51,994, female 51,759) primary and middle school students aged 6-15 years in two districts in Beijing city were surveyed from October 1987 to April 1989. The heights of the students were measured. According to the height standard of northern cities in China, 202 students with heights below the 3rd percentile for age were requested for detailed history, physical examination, screening GH test bone age, T4, SGPT, chest X-ray, routine urine test and sex chromatin (in female). If GH less than 10 micrograms/L, two provocative tests (L-dopa or clonidine and insulin hypoglycaemia test) were done. Then the heights of the short students were observed for 1/2-2 years. GHD was diagnosed in 12 cases based on the GH peak levels less than 10 micrograms/L in two provocative tests, whose growth velocity was slower than that for students of the same age and sex. Of these subjects with GHD, total GHD (GH less than 5 micrograms/L) was present in 7 and partial GHD (GH = 5-9.9 micrograms/L) in 5. The 12 GHD students (male 9, female 3) aged 8.9-15.7 years accounted for 1/8,646 in the total surveyed students. The male and female GHD accounted for 1/5,777 and 1/17,253 in the total males and females respectively.

PIP: The prevalence of growth hormone (GH) deficiency in Beijing children was estimated by measuring the heights of 103,753 children aged 6-15 and assessing those below the 3rd percentile in height. The following data were collected from 202 students: history, physical examination results, bone age, T4, chest x-ray, liver function tests, urinalysis, and sex chromatin in the girls who had not menstruated. 13 short children were excluded because of organic disease. Those with GH 10 mcg/L were subjected to provocative tests using L-dopa, clonidine, and insulin. GH deficiency was diagnosed in 12 children based on GH levels, provocative testing, and growth velocity over the next 1.5 years. There was total GH deficiency (GH 5 mcg/L) in 7 children and partial GH deficiency (GH 5-9.5 mcg/L) in 5 others. These 9 boys and 3 girls accounted for 1 case of GH deficiency/8646 middle school students in Beijing. The prevalence is between that published for Newcastle and Edinburgh, UK. This information will be useful for estimating the amount of synthetic GH needed in China.

[Autoradiographic approach to the developmental study on the binding sites of AVP4-8 in rat hippocampus].

The localization of the 35S-labelled AVP4-8 binding sites in the rat hippocampus was studied by using autoradiographic approach via observing the selective damages of hippocampal neurons by neurotoxins, and the developmental regulation of the hippocampal AVP4-8 receptor by pretreatment with exogenous AVP4-8 was observed. In adult rat hippocampus, the binding sites of AVP4-8 were assembled on the whole hippocampal pyramidal cell layer and granular cell layer of the dentate gyrus. Treatment of colchicine caused parallel disappearances of granular cells and the AVP4-8 binding sites in the gyrus, while treatment of kaininc acid destroyed the CA3-CA4 pyramidal cell layer and abolished the binding sites in this area. The developmental emergences of AVP4-8 binding sites were normally on postnatal day 6 in pyramidal cell layer and postnatal day 7 in the dentate gyrus. However, postnatal daily treatments of exogenous AVP4-8 enhanced the formations of both pyramidal and dentate binding sites, as they appeared rather densely on postnatal day 5. The characterized distribution of AVP4-8 binding sites in the rat hippocampus and the relationship between their developmental enhancements and facilitation of learning behaviors in mature rat by neonatal treatment of exogenous AVP4-8 were discussed.

[Effect of AVP(4-8) administration on Ca2+/CaM-dependent protein kinase II autophosphorylation in rat brain].

The extent increase of Ca2+/CaM-dependent protein kinase II (CaMK II) autophosphorylation in various brain regions of rat reached a maximum value, one hour after s.c. administration of AVP(4-8). The increase in the cortex amounted to 192% of the control (P < 0.001), while in the hippocampus only 40% (P < 0.05). The autophosphorylation of CaMK II was dependent on both Ca2+ and CaM. Western blotting with anti-CaMK II alpha monoclonal antibody showed that the content of CaMK II alpha in cortex did not show detectable change in 1 h as compared to the control group. ZDC(C)PR, an antagonist of AVP(4-8), markedly blocked the effect of AVP(4-8), suggesting that AVP (4-8) stimulated CaMK II autophosphorylation is mediated through its receptor.

[Chemical constituents of roots, rhizomes and stems of Amomum villosum Lour].

Ethyl octacosate, docosyl hexylate, a new compound stigmast-4-ene-1,3-dione, beta-sitosterol and daucosterol were isolated and identified from the roots and rhizomes of Amomum villosum cultivated in Xishuangbanna, Yunnan. Two compounds daucosterol and emodin monoglycoside were isolated and identified from the stems of A. villosum.

Excision of Mullerian duct remnant for persistent Mullerian duct syndrome provides favorable short- and mid-term outcomes.

OBJECTIVE: In dealing with persistent Mullerian duct syndrome (PMDS), excision of Mullerian duct remnant (MDR) has been rarely mentioned in the past, but recent discussions have taken place. This study aimed to evaluate the operative feasibility and outcomes. MATERIALS AND METHODS: Three patients with PMDS operated on with excision of MDR between 2000 and 2009 were enrolled. Medical records were retrospectively collected and reviewed. RESULTS: Bilateral undescended testis was manifested in all cases. Two patients presented with incarcerated hernia, requiring emergency herniorrhaphy at the ages of 6 months and 10 days, respectively. Reconstruction comprising simultaneous MDR excision and orchiopexy was made at the age of 1 year. MDR was incidentally found in another patient during operation for undescended testis. Immediate reconstruction was accomplished. Follow-up periods were 12.0, 3.5, and 2.5 years, respectively. Worse outcomes were noted on the two testes with repeated operations for incarcerated hernias, whereas the outcomes on the other four testes with a single operation were favorable. CONCLUSIONS: Excision of MDR is technically feasible, and provides favorable outcomes in cases of a single operation. For experienced surgeons, immediate reconstruction should be the priority when this abnormality is incidentally encountered at an age suitable for orchiopexy.

Generating ultrabroadband terahertz radiation based on the under-compression mode of velocity bunching.

We propose and analyze a scheme to generate enhanced ultrabroadband terahertz (THz) radiation through coherent transition radiation emitted by ultrashort electron beams based on a 10.5 m beamline at Tsinghua University. The proposed scheme involves the initial compression of the electron beam with a few hundred pC charges using a velocity bunching scheme (i.e., RF compression) in an under-compression mode instead of the usual critical-compression mode in order to maintain a positive energy chirp at the exit of the traveling wave accelerator. After a long drift segment, the particles in the tail catch up with the bunch head. More than 80% of the particles are distributed in a spike with an rms length less than 20 fs. Such beams correspond to an ultrabroadband coherent transition radiation (CTR) spectrum of 0.1 THz to 25 THz, with the single-pulse THz radiation energy of up to 50 µJ. The principle of CTR and under-compression mode of velocity bunching are introduced in this paper. And the ASTRA simulation parameters and the stability of the system are also discussed.