Narrow Bandwidth Gamma Comb from Nonlinear Compton Scattering Using the Polarization Gating Technique.

Nonlinear Compton scattering is a promising source of bright gamma rays. Using readily available intense laser pulses to scatter off the energetic electrons, on the one hand, allows us to significantly increase the total photon yield, but on the other hand, leads to a dramatic spectral broadening of the fundamental emission line as well as its harmonics due to the laser pulse shape induced ponderomotive effects. In this Letter we propose to avoid ponderomotive broadening in harmonics by using the polarization gating technique-a well-known method to construct a laser pulse with temporally varying polarization. We show that by restricting harmonic emission only to the region near the peak of the pulse, where the polarization is linear, it is possible to generate a bright narrow bandwidth comb in the gamma region.

Quantifying the influence of short-term emission reductions on climate.

The COVID-19 (coronavirus disease 2019) pandemic has resulted in a marked slowdown in greenhouse gas and aerosol emissions. Although the resulting emission reductions will continue to evolve, this will presumably be temporary. Here, we provide estimates of the potential effect of such short-term emission reductions on global and regional temperature and precipitation by analyzing the response of an Earth System Model to a range of idealized near-term emission pathways not considered in available model intercomparison projects. These estimates reveal the modest impact that temporary emission reductions associated with the COVID-19 pandemic will have on global and regional climate. Our simulations suggest that the impact of carbon dioxide and aerosol emission reductions is actually a temporary enhancement in warming rate. However, our results demonstrate that even large emission reductions applied for a short duration have only a small and likely undetectable impact.

North Atlantic climate far more predictable than models imply.

Quantifying signals and uncertainties in climate models is essential for the detection, attribution, prediction and projection of climate change1-3. Although inter-model agreement is high for large-scale temperature signals, dynamical changes in atmospheric circulation are very uncertain4. This leads to low confidence in regional projections, especially for precipitation, over the coming decades5,6. The chaotic nature of the climate system7-9 may also mean that signal uncertainties are largely irreducible. However, climate projections are difficult to verify until further observations become available. Here we assess retrospective climate model predictions of the past six decades and show that decadal variations in North Atlantic winter climate are highly predictable, despite a lack of agreement between individual model simulations and the poor predictive ability of raw model outputs. Crucially, current models underestimate the predictable signal (the predictable fraction of the total variability) of the North Atlantic Oscillation (the leading mode of variability in North Atlantic atmospheric circulation) by an order of magnitude. Consequently, compared to perfect models, 100 times as many ensemble members are needed in current models to extract this signal, and its effects on the climate are underestimated relative to other factors. To address these limitations, we implement a two-stage post-processing technique. We first adjust the variance of the ensemble-mean North Atlantic Oscillation forecast to match the observed variance of the predictable signal. We then select and use only the ensemble members with a North Atlantic Oscillation sufficiently close to the variance-adjusted ensemble-mean forecast North Atlantic Oscillation. This approach greatly improves decadal predictions of winter climate for Europe and eastern North America. Predictions of Atlantic multidecadal variability are also improved, suggesting that the North Atlantic Oscillation is not driven solely by Atlantic multidecadal variability. Our results highlight the need to understand why the signal-to-noise ratio is too small in current climate models10, and the extent to which correcting this model error would reduce uncertainties in regional climate change projections on timescales beyond a decade.

Sensible heat has significantly affected the global hydrological cycle over the historical period.

Globally, latent heating associated with a change in precipitation is balanced by changes to atmospheric radiative cooling and sensible heat fluxes. Both components can be altered by climate forcing mechanisms and through climate feedbacks, but the impacts of climate forcing and feedbacks on sensible heat fluxes have received much less attention. Here we show, using a range of climate modelling results, that changes in sensible heat are the dominant contributor to the present global-mean precipitation change since preindustrial time, because the radiative impact of forcings and feedbacks approximately compensate. The model results show a dissimilar influence on sensible heat and precipitation from various drivers of climate change. Due to its strong atmospheric absorption, black carbon is found to influence the sensible heat very differently compared to other aerosols and greenhouse gases. Our results indicate that this is likely caused by differences in the impact on the lower tropospheric stability.

Understanding Rapid Adjustments to Diverse Forcing Agents.

Rapid adjustments are responses to forcing agents that cause a perturbation to the top of atmosphere energy budget but are uncoupled to changes in surface warming. Different mechanisms are responsible for these adjustments for a variety of climate drivers. These remain to be quantified in detail. It is shown that rapid adjustments reduce the effective radiative forcing (ERF) of black carbon by half of the instantaneous forcing, but for CO2 forcing, rapid adjustments increase ERF. Competing tropospheric adjustments for CO2 forcing are individually significant but sum to zero, such that the ERF equals the stratospherically adjusted radiative forcing, but this is not true for other forcing agents. Additional experiments of increase in the solar constant and increase in CH4 are used to show that a key factor of the rapid adjustment for an individual climate driver is changes in temperature in the upper troposphere and lower stratosphere.

PDRMIP: A Precipitation Driver and Response Model Intercomparison Project, Protocol and preliminary results.

As the global temperature increases with changing climate, precipitation rates and patterns are affected through a wide range of physical mechanisms. The globally averaged intensity of extreme precipitation also changes more rapidly than the globally averaged precipitation rate. While some aspects of the regional variation in precipitation predicted by climate models appear robust, there is still a large degree of inter-model differences unaccounted for. Individual drivers of climate change initially alter the energy budget of the atmosphere leading to distinct rapid adjustments involving changes in precipitation. Differences in how these rapid adjustment processes manifest themselves within models are likely to explain a large fraction of the present model spread and needs better quantifications to improve precipitation predictions. Here, we introduce the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), where a set of idealized experiments designed to understand the role of different climate forcing mechanisms were performed by a large set of climate models. PDRMIP focuses on understanding how precipitation changes relating to rapid adjustments and slower responses to climate forcings are represented across models. Initial results show that rapid adjustments account for large regional differences in hydrological sensitivity across multiple drivers. The PDRMIP results are expected to dramatically improve our understanding of the causes of the present diversity in future climate projections.

[Polymorphism and structure of the population of Proteocephalus longicollis Zeder, 1800 (Cestoda: Proteocephalidae) in the vendace Coregonus albula L]. / Polimorfizm i struktura populiatsii Proteocephalus longicollis zeder, 1800 (Cestoda: Proteocephalidae) iz evropeiskoi riapushki Coregonus albula L.

Polymorphism and phenotypic diversity of a hostal ecoform of Proteocephalus longicollis from its typical host, the vendace, Coregonus albula L., were studied. A complex phenotypic structure of the parasite population and presence of morphologically different groupings were revealed. We distinguished four groupings based on the external characters and three groupings based on the feed and reproduction features; among latter groupings one has very specific variations of features. We conclude that P. longicollis has high intraspecific and intrapopulation heterogeneity, and the host plays a stabilising role in the parasite species formation.

[UHF-dielectrometry in the assessment of the structural organization of salt solutions and interstitial fluids in normal and cicatricial tissues]. / KVCh-diélektrometriia pri otsenke strukturnoi organizatsii rastvorov solei i tkanevykh zhidkostei zdorovoi i rubtsovoi tkani.

The complex dielectric permittivity of salt solutions with positive and negative salvation as well as healthy and cicatricially changed human skin in situ at the frequencies of 42 and 56.6 GHz was measured. The relation between the dielectric characteristics of water and diluted salt solutions and changes in their structural organization conditioned by different temperatures of samples and the type of salvation of electrolytes was studied. The differences in the dielectric characteristics of healthy and cicatricially changed skin are interpreted in terms of the dependence of the structural organization of interstitial fluids on the morphological and functional state of biological tissues.

[Phenotype structure and its dynamics at different stages of the reproductive period of Proteocephalus osculatus (Cestoda: Proteocephalidae)--a parasite of catfish (Silurus glanis L.)]. / Fenotipicheskaia struktura i ee dinamika na raznykh étapakh reproduktivnogo perioda Proteocephalus osculatus (Cestoda: Proteocephalidae)--parazita soma Silurus glanis L.

Discrete variability of four P. osculatus characteristics descriptive of cestodes' major functional complexes: attachment and trophic-reproduction, was determined. Phenotypic diversity of P. osculatus from 2 samples collected at different stages of the population reproductive period was analysed. Unequal adaptation of phenotypes to the ambient conditions was hypothesised.

[Study of water exchange in skin tissues by microwave dielectrometry]. / Izuchenie vodnogo obmena tkanei kozhi metodom KVCh-diélektrometrii.

The complex dielectric permitivity of human skin was measured at a frequency of 42 GHz, and a method for calculating water content in skin tissues in vivo was proposed. The water content reaction of skin to standard physical exercises and nontoxic doses of nicotine was investigated. The functionally related changes in skin dielectric properties were interpreted as structural rearrangements of water contained in blood and tissues fluids.

Use of spinal manipulative therapy in the treatment of duodenal ulcer: a pilot study.

OBJECTIVE: To evaluate the effectiveness of spinal manipulative therapy (SMT) in the treatment of an internal organ disorder. DESIGN: Clinical trial. SETTING: Medical hospital. PATIENTS: Eleven adult men and women ranging in age from 18-44 yr with endoscopically confirmed diagnosis of ulcer disease took part in the study as an experimental group. The outcome of 24 cases of uncomplicated ulcerous disease treated by usual medical methods was analyzed as a control. INTERVENTIONS: The experimental group received spinal manipulative therapy (SMT) treatment from 5-22 days with a range of 3-14 procedures. The control group received traditional medical treatment (drug therapy and diet). The dietary regimen was standard for both groups. MEASUREMENTS: The effectiveness of the treatment was evaluated using clinical parameters and endoscopic examination performed weekly. MAIN RESULTS: The use of SMT resulted in pain relief after 1-9 (avg. 3.8) days and clinical remission an average of 10 days earlier than traditional care. CONCLUSIONS: Chiropractic practice often includes patients with gastrointestinal problems who report some relief of their symptoms after treatment; however, the physiological basis for these results has yet to be established. The normalization in segmental trophic innervation of the mucosal layer of the intestine, and positive reaction of the whole body, are under discussion as a possible mechanism for the treatment effect.

[The role of the mononuclear phagocyte system in the pathogenesis of excessive peritoneal adhesions in children with peritonitis]. / Znachenie sistemy mononuklearnykh fagotsitov v patogeneze izbytoch- nogo spaikoobrazovaniia pri peritonite u detei.

A study was made of the significance of mononuclear phagocytes in the outcome of post-inflammatory++ peritoneal repair and onset of peritoneal adhesions. It has been revealed that patients with adhesions occurring in the postoperative period manifest insufficiency of the macrophagal response characterized by a decrease of the content of macrophagal elements in peritoneal exudate and derangement of macrophagal migration in the skin fenestra test during reproduction of aseptic inflammation. It is assumed that stimulation of mononuclear phagocytes can serve a means for preventing peritoneal adhesions.

[Flowmetry in the evaluation of hemodynamics of the lower limbs in chronic ischemia]. / Floumetricheskaia otsenka gemodinamiki nizhnykh konechnostei pri khronicheskoi ishemii.

Regional hemodynamics in the lower limbs was studied in 250 patients (480 lower limbs) with obliterative lesions of the abdominal aorta and lower limb arteries. Six levels of blood circulation were examined: the iliac segment, the femoral segment, the popliteal and tibial segments, the circulatory channels of the foot and toes. The suggested complex method of ultrasonic measurement of the blood flow in the lower limbs makes it possible to evaluate the hemodynamic significance of the collaterals and the adverse effect of the pathologically changed arterial segment on the regional hemodynamics. The conducted noninvasive study of hemodynamics allows the initial stages of the lesion to be detected (which physical examination fails to do in some cases) and adequate tactics of stage-by-stage treatment by surgery to be elaborated. The outcome of the reconstructive operation can be prognosed by determining the patency of the arterial arch of the foot and the leg arteries.

[Non-invasive diagnosis of occlusive lesions of the aorto-femoral segment]. / Neinvazivnaia diagnostika okkliuziruiushchikh porazhenii aortobedrennego segmenta.

A device is proposed for a noninvasive examination of hemodynamics of the aorto-femoral segment which allows to make compression of the arteries under the inguinal ligament. The arterial pressure is measured with an ultrasonic sensor under decompression of the pneumatic balloon. Under examination there were 369 patients. The examination has revealed different stages of stenosis of the iliac segment from the initial symptoms (50% stenosis) up to a pronounced stenosis. The occlusion of iliac arteries was diagnosed and collateral circulation was quantitated.