Real-time visualization of the laser-plasma wakefield dynamics.

The exploration of new acceleration mechanisms for compactly delivering high-energy particle beams has gained great attention in recent years. One alternative that has attracted particular interest is the plasma-based wakefield accelerator, which is capable of sustaining accelerating fields that are more than three orders of magnitude larger than those of conventional radio-frequency accelerators. In this device, acceleration is generated by plasma waves that propagate at nearly light speed, driven by intense lasers or charged particle beams. Here, we report on the direct visualization of the entire plasma wake dynamics by probing it with a femtosecond relativistic electron bunch. This includes the excitation of the laser wakefield, the increase of its amplitude, the electron injection, and the transition to the beam-driven plasma wakefield. These experimental observations provide first-hand valuable insights into the complex physics of laser beam-plasma interaction and demonstrate a powerful tool that can largely advance the development of plasma accelerators for real-time operation.

Femtosecond electron microscopy of relativistic electron bunches.

The development of plasma-based accelerators has enabled the generation of very high brightness electron bunches of femtosecond duration, micrometer size and ultralow emittance, crucial for emerging applications including ultrafast detection in material science, laboratory-scale free-electron lasers and compact colliders for high-energy physics. The precise characterization of the initial bunch parameters is critical to the ability to manipulate the beam properties for downstream applications. Proper diagnostic of such ultra-short and high charge density laser-plasma accelerated bunches, however, remains very challenging. Here we address this challenge with a novel technique we name as femtosecond ultrarelativistic electron microscopy, which utilizes an electron bunch from another laser-plasma accelerator as a probe. In contrast to conventional microscopy of using very low-energy electrons, the femtosecond duration and high electron energy of such a probe beam enable it to capture the ultra-intense space-charge fields of the investigated bunch and to reconstruct the charge distribution with very high spatiotemporal resolution, all in a single shot. In the experiment presented here we have used this technique to study the shape of a laser-plasma accelerated electron beam, its asymmetry due to the drive laser polarization, and its beam evolution as it exits the plasma. We anticipate that this method will significantly advance the understanding of complex beam-plasma dynamics and will also provide a powerful new tool for real-time optimization of plasma accelerators.

"Struggling to Remain Relevant": Why and How Radicalization Was Impeded in the Struggle against the Gaza Pullout.

The role of cognitive mechanisms in processes of radicalization cannot be overestimated. However, focusing solely on violence-prone values and ideologies without examining how they gain and lose consequentiality in the context of relational dynamics, hampers our understanding of the shift from support for, to actual engagement in political violence. Using a case of nonradicalization-the predominantly nonviolent struggle of Jewish settlers against the Gaza Pullout (2004 to 2005)-this paper accounts for the process whereby despite the presence of violence-prone values and ideologies we observe little engagement in political violence. Findings from a mechanism-based, mixed-method design that includes content analysis, in-depth interviews, network analysis, and contention-repression data, reveal how the combined operation of the reversals of relational mechanisms mitigate the salience of cognitive mechanisms and, consequently, impede radicalization on the part of militant Jewish settler organizations. The contributions of the findings to a relational theory of radicalization are discussed in the conclusion.

Body composition and reproductive performance at entry into lay of anno 1980 versus anno 2000 broiler breeder females under fast and slow release from feed restriction.

During the 1990s, various disturbances arose affecting broiler breeder females at entry into lay. These disturbances were associated with even slight overfeeding during release of feed restriction in this critical maturation period. The present experiment was carried out to gain some insight into the causes of these disturbances by comparing the effect of fast (FF) and slow (SF) release from feed restriction at entry into lay in 2 broiler breeder populations: B1980, representing the genetic level of 1980, and B2000, the genetic level of 2000. Under the FF treatment, B1980 entered lay 19.2 d earlier than B2000; this increased to 37.4 d earlier under SF. The B1980 population entered lay at virtually the same mean age for SF and FF, whereas B2000 entered lay 15.7 d earlier under the FF. Body weight at first egg were 2,621 g for the B1980 and 3,591 g for B2000. Differences in BW at first egg between feeding treatments within lines were minor. As a percentage of BW, ovary, oviduct, and follicle weights were the same for B1980 and B2000; breast weight was 14.9% for B1980 and 21.2% for B2000; abdominal fat pad weight was 5.37% for B1980 and 2.67% for B2000. Follicle weight and absolute difference in weight between successive follicles was greater in B2000 than in B1980. It is concluded that body fat content does not limit entry into lay, and that threshold BW for onset of sexual maturity of broiler breeder hens increased by about 1,000 g between 1980 and 2000, indicating a tight association between juvenile growth rate and threshold BW for onset of sexual maturity. It is also concluded that disturbances at entry into lay due to overfeeding are not due to smaller differences between successive follicles in B2000 compared with B1980. There are hints, however, that overfeeding may contribute to these disturbances by decreasing differences between successive follicles.

Effect of photoperiod and quantitative feed restriction in a broiler strain on onset of lay in females and onset of semen production in males: a genetic hypothesis.

The effects of feed restriction and photoperiod on body weight (WTSXM) and age (ASXM) at onset of mature semen production in males and onset of lay in females of a broiler female line were examined. Feeding treatments were as follows: ad libitum (AL) and quantitative feed restriction (QR). Photoperiod treatments were as follows: open shed (OS), in which the chicks were reared under naturally increasing daylight with supplemental light; dark room (DR), in which chicks were reared under short days, gradually increasing from 6 h of light (L) to 11.5L; and dark room to open shed (DR-OS), in which chicks reared under short days in the dark room were transferred to the open shed at 149 d. Treatment effects were similar in direction in males and females, suggesting similar control of entry into reproduction of the two sexes, although within a given treatment, males matured earlier than females. Effects of feeding and photoperiod treatments were additive. Relative to QR, the AL feeding treatment increased WTSXM by 832 g for males and 1,089 g for females; ASXM was decreased by 15.8 d for males and 9.3 d for females. Relative to OS, the DR photoperiod increased WTSXM by 591 g for males and 513 g for females; ASXM was increased by 17.5 d for males and 26.8 d for females. The DR-OS photoperiod increased WTSXM by 86 and 169 g for males and females, respectively; ASXM was increased by 6.1 d and 4.9 d, respectively. Under DR, the delay in onset of sexual maturity caused by QR was not due to failure to reach threshold body weight or age and, hence, appears to have resulted from the feed restriction itself. A similar delay for QR was found under OS but might have been due to failure to reach threshold body weight. It is speculated that the delay in onset of sexual maturity caused by feed restriction may be an ecological adaptation or, alternatively, a result of nutritional imbalance.

Two-way selection for high and low responsiveness to photostimulation in broiler strain males.

Previous studies indicate that responsiveness to photoperiod (PR) has deteriorated in White Rock heavy breed females and males, and that selection for increased PR in females has a positive effect on egg production. In order to determine whether PR can be affected by selection in males, a two-way selection experiment for high and low PR, as expressed through early and late onset of mature semen production under suboptimal photoperiod, was implemented in White Rock heavy breed males. In each selection line, the selected males in each generation were mated to unselected females of the same line. After four generations of selection, males and females of the two selection lines did not differ significantly in 6-wk body weight. Males of the high-PR line, however, achieved mature semen production 18.9 d earlier (P < 0.01) and at a body weight 587 g lighter (P < 0.01) than the males of the low-PR line. Females of the high-PR line came into lay 25.9 d earlier (P < 0.01) and at a body weight 375 g lighter (P < 0.01) than females of the low-PR line; they also produced 13.9 more eggs over a 14-wk test period (P < 0.01). These results show that it is possible to affect PR by selection in males, with parallel effects on female PR and reproductive performance. This result carries the potential of improving reproductive performance of male and female broiler chickens through mass selection for early sexual maturity among males.

Simple sequence repeats in Escherichia coli: abundance, distribution, composition, and polymorphism.

Computer-based genome-wide screening of the DNA sequence of Escherichia coli strain K12 revealed tens of thousands of tandem simple sequence repeat (SSR) tracts, with motifs ranging from 1 to 6 nucleotides. SSRs were well distributed throughout the genome. Mononucleotide SSRs were over-represented in noncoding regions and under-represented in open reading frames (ORFs). Nucleotide composition of mono- and dinucleotide SSRs, both in ORFs and in noncoding regions, differed from that of the genomic region in which they occurred, with 93% of all mononucleotide SSRs proving to be of A or T. Computer-based analysis of the fine position of every SSR locus in the noncoding portion of the genome relative to downstream ORFs showed SSRs located in areas that could affect gene regulation. DNA sequences at 14 arbitrarily chosen SSR tracts were compared among E. coli strains. Polymorphisms of SSR copy number were observed at four of seven mononucleotide SSR tracts screened, with all polymorphisms occurring in noncoding regions. SSR polymorphism could prove important as a genome-wide source of variation, both for practical applications (including rapid detection, strain identification, and detection of loci affecting key phenotypes) and for evolutionary adaptation of microbes.

Comb size and estrogen levels toward the onset of lay in broiler and layer strain females under ad libitum and restricted feeding.

The time course of comb development and estrogen levels were compared in broiler (BX) and layer (LX) females that consumed feed ad libitum (A) or were subjected to quantitative feed restriction (R). The chicks were reared under short photoperiod [(6 h light (L):18 h dark (D)] until 22 wk of age. At this time, photoperiod was increased in one step to 8L:16 D, and then gradually increased until 14L:10D at 34 wk. There was a significant interaction between genetic type and feeding treatment, such that entry into lay of the LX-R and BX-R females was delayed by 1 and 4 wk, respectively, relative to the LX-A and BX-A birds. Mean comb size of LX-A birds began to increase while still under 6L:18D photoperiod; that of the other treatment groups did not begin to increase until photoperiod was shifted to 8L:16D. Comb size of individual LX-A, LX-R, and BX-A birds began to increase about 8 wk prior to individual onset of lay; that of BX-R birds about 11 wk prior to onset of lay. In all groups, estrogen levels remained low until 3 to 4 wk prior to onset of lay, when they showed a sharp increase. Following onset of lay, estrogen levels of all groups remained high. Critical day length of LX-A birds appears to be lower than that of BX-A birds. In addition, feed restriction per se appears to decrease photoperiod responsiveness of BX birds.

Selection for high and low threshold body weight at first egg in broiler strain females. 7. Effect of photoperiod on body weight and age at onset of mature semen production, in males of the selection lines, and in commercial broiler and layer males.

Effect of photoperiod on age and BW at attainment of mature semen production was examined in males of lines selected for high (HL) and low (LL) threshold BW at onset of lay, and in males of a commercial Cornish male line (MC), a commercial broiler breeder female line cross (BX), and a commercial layer cross (LX). Photoperiod treatments were: I, increasing natural spring light; and D, steadily decreasing artificial light provided in a light-controlled room. Under I, age at onset of mature semen production was 168.5, 133.6, 138.1, 124.0, and 118.0 d for HL, LL, MC, BX, and LX males, respectively. Under D, age at onset of mature semen production increased by 18.3, 8.0, 55.9, 60.9, and -2.0 d, respectively. The differential effect of Treatment D on the various genetic stocks is attributed to differences between stocks in photoperiodic drive. Therefore, the very great increase in age at onset of mature semen production in BX and MC males points to a severe reduction in photoperiodic drive in males of these stocks, and to future problems in male fertility in broiler breeder flocks entering lay in the summer and fall. Lines HL, LL, BX, and LX rank the same with respect to photoperiodic drive, whether measured in males as in this experiment, or in females, as in a previous experiment. This result suggests that genetic factors affecting photoperiodic drive come to similar expression in males and females. Thus, selection for increased photoperiodic drive in broiler line males may be able to increase photoperiodic drive in broiler line females, and in this way improve female reproductive performance.

Selection for high and low threshold body weight at first egg in broiler strain females. 6. Threshold weight for onset of photosensitivity in females of the selection lines.

A two-way selection program, carried out for high and low threshold BW at onset of lay (TWL) resulted in a marked difference in TWL in the selected lines. Later studies showed that the selection procedure had decreased photoperiodic drive in the high line (HL) as compared to the low line (LL), in this way increasing the number of days required from onset of photosensitivity to onset of lay in the HL as compared to the LL. The present study was carried out to determine whether the difference in photoperiodic drive was sufficient to account for the entire difference in TWL between the HL and LL, or whether it is also necessary to postulate a difference in threshold weight for onset of photosensitivity (TWSM) as well. Birds of the two lines were raised under feed restriction to 22 wk reaching weights (1,881.8 g) for LL, 2,304.8 g for HL), well below anticipated TWSM. They were then provided gradually increasing amounts of feed, resulting in daily gains of 3 to 5 g for the LL and 8 to 9 g for the HL. Under this regimen, the HL entered lay an average of 64.4 d later and at a body weight 752.8 g greater than the LL. On the basis of previous studies of these lines, of the 64.4 d delay in onset of lay in the HL as compared to LL, 21 d can be attributed to the difference in photoperiodic drive. The excess of 43 d must thus represent a difference in TWSM. During this period the HL were gaining about 8.5 g/d, and at 22 wk HL body weight was already 153 g greater than LL body weight. In all then, TWSM of HL is estimated at 518 g greater than that of the LL. Thus, the selection procedure employed for TWL apparently affected TWSM as well as photoperiodic drive.

Two-way selection for threshold body weight at first egg in broiler strain females. 5. Replication of results in a two-generation selection experiment.

Selection for high and low threshold weight for onset of lay (ThrWtLay), carried out in a broiler line over six generations, was previously found to increase reproductive performance in the low line (LL). Because of the potential importance of this effect, a two-generation replication of the original experiment was carried out using a modern broiler line. Selection was on the basis of ThrWtLay, measured as body weight at first egg, following gradual release from feed restriction. The total response to selection over two generations was 382 g, giving a realized heritability of .42. The difference in 6-wk body weight of the two lines was +19 g in favor (P > .05) of the high line (HL). Reproductive performance was measured in the S2 generation and in the first (R1) generation of relaxed selection. On the average, age at first egg of LL was 17.6 d earlier, and prepeak, postpeak, and total egg production of LL to a fixed age was 9.9, 1.1, and 11.1 eggs greater, respectively, than that of HL. The differences in age at first egg, prepeak, and total egg production were significant; those in postpeak production were not. There was a difference of 1.1 g in favor (P > .05) of HL for egg weight. Thus, the results of this short-term selection experiment are broadly consistent with those of the original, long-term selection. Namely, ThrWtLay responded strongly to selection, with a powerful accompanied response in age at onset of lay and in prepeak egg production, and only a small effect on 6-wk body weight. However, in contrast to the results obtained previously, LL in the present experiment showed only a small increase (P > .05) in postpeak production relative to HL. Nevertheless, although an effect on postpeak production was not obtained in the present experiment, the results do provide general support for the previously expressed view that selection for early onset of lay, on release from feed restriction, may provide a means of increasing photoperiodic drive and consequent reproductive performance of broiler breeders.

Selection for high and low threshold body weight at first egg in broiler strain females. 4. Photoperiodic drive in the selection lines and in commercial layers and broiler breeders.

A two-way selection program, carried out for high and low threshold BW at onset of lay (ThrWtLay), decreased photoperiodic drive of the high line (HL) relative to the low line (LL). Photoperiodic drive in modern broiler breeder females was compared to layer females in experiments using the HL and LL lines, a commercial layer cross (LX), and a commercial broiler breeder female line cross (BX). Treatment groups were: NS, natural decreasing light to 20 wk, followed by natural light supplemented to 16 h daily with artificial light; NN, natural decreasing light to end of experiment; DD, dark room from hatch to end of experiment; ND, natural decreasing light to 20 wk, dark room thereafter. Under NS, mean age and BW at first egg was greater for the HL line than for the LL line. The difference increased by a further 8.9 d and 217.5 g under NN. Similarly, under NS, mean age and BW at first egg was greater for BX than for LX, and the difference increased by a further 22.6 d and 256.1 g under NN. These interactions indicate greater photoperiodic drive of LX and LL stocks relative to the HL and BX stocks. Prepeak and peak egg production (EP) was greatest for the LX, lower for the LL, and lower yet for HL and BX. Photoperiodic drive may be of major importance in determining prepeak and peak EP. Except for the DD treatment, age and BW of the LX cross at first egg were virtually identical across treatments, those of the LL line were similar, whereas those of the HL and BX stocks showed differences. Similarly, EP curves of the LX cross were virtually identical across treatments, those of the LL line were relatively uniform, but those of the HL and BX stocks again showed great differences. Standard deviation and coefficient of variation of peak EP were very low for the LX cross, still low, but significantly greater for the LL line, and significantly greater yet again for both HL and BX stocks. Thus, increased photoperiodic drive may also be associated with greater stability of reproductive performance. Selection for early onset of lay on release from feed restriction may provide a means of increasing photoperiodic drive and consequent reproductive performance of broiler breeders.

In vitro and in vivo anticalcification effects of novel bishydroxyiminophosphonates.

Some geminal bisphosphonates are used clinically for a number of important bone- and/or calcium-related diseases; however, side effects and lack of selectivity impede their wide use. This work reports the synthesis and evaluation of bishydroxyiminophosphonates (e.g., adipoyl- and suberoylbisphosphonate dioximes). These compounds significantly inhibited hydroxyapatite formation and dissolution in vitro and the calcification of bioprosthetic tissue implanted subdermally in rats. The compounds reported in this paper are less active than the structurally related bisacylphosphonates. The results of this work indicate that the introduction of oxime groups adjacent to the phosphonic function in long-chain bisphosphonates confers calcium interaction capabilities and that complete ionizability of a bisphosphonate may enhance its biological activity.

Measurement of serum [3H]tetracycline kinetics and indices of kidney function facilitate study of the activity and toxic effects of bisphosphonates in bone resorption.

The [3H]tetracycline ([3H]TC) model is based on the observation that TC is released from the bones of rats prelabeled with [3H]TC via first-order kinetics, a factor directly reflecting the kinetics of bone resorption. In the present paper we applied the [3H]TC elimination model to rats treated with antiresorptive drugs. The validity of this model was evaluated by examining the effect of the bisphosphonate, 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (ABP), and a novel bisphosphonate, dihydrogen disodium adipoylbisphosphonate (AdBP), on serum TC levels and the elimination rate constant. ABP and AdBP significantly inhibited the TC elimination rate. However, ABP treatment caused impairment of bone mineralization, renal dysfunction, and inhibition of somatic growth. It is concluded that antiresorptive effects of bisphosphonates could be evaluated by the [3H]TC model, but this model is limited to animals with normal kidney function. The experimental conditions provide a technically simple method which is sensitive enough to examine antiresorptive properties in a healthy animal and to detect adverse effects on the kidney. The activity of the novel bisacylphosphonate, AdBP, and lack of its adverse effects indicate the potential of this drug for clinical applications.

Two-way selection for threshold body weight at first egg in broiler strain females. 2. Effect of supplemental light on weight and age at first egg.

In order to undergo the processes leading to lay, female chickens must reach a minimum threshold age and body weight, and be exposed to some minimum amount of light stimulation. By two-way selection over six generations lines were developed that differed markedly in body weight at first egg. The effect of supplemental light on age and body weight at first egg of these lines was studied in two experiments. In the first experiment, birds of the two lines were provided ad libitum access to feed from hatch, reaching the weight threshold at an early age. Supplemental light was provided at either 91 or at 126 days of age (before or after the age threshold, respectively). Differences in body weight and age at first egg of the two lines were the same in both light treatments. In the second experiment, birds of the two lines were raised under feed restriction to 154 days of age and then released to ad libitum feeding under supplemental or natural (autumn) light. Differences between the lines in age and weight at first egg were greater in the group maintained under natural light than under supplemental light. The results are interpreted in terms of a model relating age at first egg to weight and age thresholds for onset of competence to respond to light stimulation, and to cumulative light stimulation required from onset of competence to first egg. It is proposed that selection affected the total amount of light stimulation required from onset of competence to onset of lay, but did not affect weight or age thresholds for onset of competence.

Selection for high and low threshold body weight at first egg in broiler strain females. 1. Direct response to selection and correlated effects on juvenile growth rate and age at first egg.

A selection program for high and low threshold body weight at first egg was carried out in a broiler line. Selection was on the basis of weight at first egg, following gradual release from feed restriction at a relatively advanced age. After six generations of selection, the lines differed by 862 g in the trait under selection. In addition, 6-wk body weight of high-line (HL) birds was 91 g greater, and age at first egg was 32 days greater than in low-line (LL) birds. When raised under an ad libitum feeding regimen from hatch, HL birds entered lay 20 days later than LL birds. When onset of lay was markedly delayed by maintaining feed restriction until 29 wk of age, body weight at first egg of HL birds was greater by 645 g than that of LL birds. Similarly, when birds of the two lines were subjected to forced molt and brought to a body weight well below that of initial body weight at first egg, and then allowed to gain weight and reenter lay, body weight difference at first egg of HL and LL birds following rehabilitation was similar to that found on original entry into lay. It is proposed that the results may most plausibly be explained as resulting from a primary effect of the selection procedure on the time required to first egg from onset of sexual competence, defined as onset of responsiveness to lay-inducing factors such as light. Alternative explanations involve effects of the selection procedure on threshold weight or threshold age requirements for sexual competence.

Minimum weight for onset of sexual maturity in female chickens: heritability and phenotypic and genetic correlations with early growth rate.

The heritability of minimum weight for onset of sexual maturity in chickens (WTSXM) and its phenotypic and genetic correlations with early growth rate were studied in a Leghorn (L) layer stock, in two White Rock (WR) broiler stocks, and in the F4, F5, and F6 segregating generations of a White Rock X Leghorn (WR X L) cross. Mean heritability of WTSXM was .38 in the WR populations and .84 in the WR X L cross populations. Mean WTSXM of the various genetic stocks were closely related to their mean early growth rate. The mean phenotypic correlation of WTSXM and early growth rate was .07 in the WR populations but .47 in the WR X L cross populations. Estimates of the genetic correlation of WTSXM with early growth rate were high, and uniform in sign in the WR X L cross populations but smaller in magnitude and variable in sign in the WR populations. The implications of these results with respect to WTSXM as a breeding objective are discussed.

Effect of diet and early quantitative feed restriction on the minimum weight requirement for onset of sexual maturity in white rock broiler breeders.

The effect of diet and feed restriction on minimum weight for onset of sexual maturity was studied in White Rock broiler breeders. In the restriction experiment, three groups of birds were subjected to moderate, severe, and very severe quantitative food restriction during the rearing period (19 week target weights: 1900, 1300, and 700 g, respectively). From 20 to 24 weeks body weight was equalized at 2200 g, and from 24 weeks birds were allowed to gain about 150 g/week until first egg. In the diet experiment, two groups of birds were raised under severe quantitative food restriction during the rearing period and then allowed to gain about 150 g/week on a low metabolizable energy/protein (ME/P) ratio diet (25.4% protein, ME/P = 116) and on a high ME/P ratio (14.7% protein, ME/P = 219) until first egg. All birds were killed at first egg. Birds of the three restriction groups entered lay at the same lean body weight and ash and protein content, but at different age, carcass weight, shank length, dry matter, and fat content. Birds of the two diet groups entered lay at the same lean body weight, shank length, and ash content but at different carcass weight, dry matter, and fat content. Considering both experiments together, birds of the different treatment groups entered lay at similar lean body weight and ash content but differed in age, carcass weight, shank length, dry matter, and fat content.(ABSTRACT TRUNCATED AT 250 WORDS)

Compensatory growth and sexual maturity in broiler females reared under severe food restriction from day of hatching.

1. Compensatory growth and the onset of lay were studied in White Rock broiler females severely restricted in food intake from day of hatching. 2. When changed to feeding ad libitum the restricted birds gained weight rapidly, but stabilised at a mean body weight 500 to 700 g less than that of controls fed ad libitum. Egg production was similar to that of controls. 3. Birds maintained at low mean body weight ( 2 224 g at 42 weeks) by continued restriction did not come into lay. In groups maintained at somewhat higher mean body weights (2 300 to 2 700 g) for period of up to a year, some birds came into lay. 4. Birds fed ad libitum showed accelerated development of comb, ovary and oviduct and weighed 2 300 to 2 700 g between 14 and 15 weeks of age, but did not come into lay until 20.5 weeks of age. 5. These results suggest that a minimum body weight and age may be required for the onset of lay in this strain.