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A number of electron beam vacuum devices such as small radiofrequency (RF) linear accelerators (linacs) and microwave traveling wave tubes (TWTs) utilize slow wave structures which are usually rather complicated in production and may require multi-step brazing and time consuming tuning. Fabrication of these devices becomes challenging at centimeter wavelengths, at large number of cells, and when a series or mass production of such structures is required. A hybrid, metal-dielectric, periodic structure for low gradient, low beam current applications is introduced here as a modification of Andreev’s disk-and-washer (DaW) structure. Compensated type of coupling between even and odd TE01 modes in the novel structure results in negative group velocity with absolute values as high as 0.1 c –0.2 c demonstrated in simulations. Sensitivity to material imperfections and electrodynamic parameters of the disk-and-ring (DaR) structure are considered numerically using a single cell model. [ABSTRACT FROM AUTHOR]

Efforts to increase the coupling coefficient of a biperiodic accelerating structure without deteriorating a high effective shunt impedance and other electrodynamic characteristics are discussed. [ABSTRACT FROM AUTHOR]

The article focuses on the addition of bis(pentafluorophenyl)phosphinous acid (BPFPPA) to different compounds having activated carbon-carbon double bond for the synthesis of tertiary P,P-bis(pentafluorophenyl) phosphine oxides. It mentions that BPFPPA can exist in both tautomeric forms and is stable in the solid state as well as in solutions in organic solvents. It also discusses the effect of the addition of BPFPPA to an unsaturated compound in chloroform.

Components of a radio-frequency system for deflecting structures of the S-frequency range, which are included in the electron-beam diagnostic complexes for a free-electron laser (XFEL, Germany), were designed. Waveguide-coaxial and waveguide-strip directional couplers, a waveguide absorbing load, a waveguide window, and an E-bend were developed. A connecting element between two deflecting structures in the form of a U-shaped rectangular-waveguide section was also calculated. [ABSTRACT FROM AUTHOR]

Background Anal cancer is a rare disease, constituting 0.5% of new cancer cases in the United States. The most common subtype is squamous cell carcinoma (scc). Studies in several developed nations have reported on an increasing incidence of anal cancer in recent decades, and various risk factors pertaining to the pathogenesis of the disease have been identified, including infection with the human papillomavirus, tobacco use, and immunosuppression. The epidemiology and distribution of anal scc throughout Canada remain poorly understood, however. Methods Using 3 population-based cancer registries, a retrospective analysis of demographic data across Canada for 1992-2010 was performed. The incidence and mortality for anal scc was examined at the levels of provinces, cities, and the forward sortation area (FSA) component (first 3 characters) of postal codes. Results During 1992-2010, 3720 individuals were diagnosed with anal scc in Canada; 64% were women. The overall national incidence rate was 6.3 cases per million population per year, with an average age at diagnosis of 60.4 years. The incidence increased over time, with significantly higher incidence rates documented in British Columbia and Nova Scotia (9.3 cases per million population each). Closer examination revealed clustering of cases in various urban centres and self-identified lgbtq communities in Toronto, Montreal, and Vancouver. Discussion This study provides, for the first time, a comprehensive analysis of the burden of anal scc in Canada, identifying susceptible populations and shedding light onto novel avenues of research to lower the incidence of anal cancer throughout the country. [ABSTRACT FROM AUTHOR]

Background Although the pathogenesis and epidemiology of endemic Burkitt lymphoma (bl) have been extensively studied, the epidemiologic landscape of sporadic and immunodeficiency-associated bl in North America remains poorly understood. Methods We used 3 distinct population-based cancer registries to retrospectively study bl incidence and mortality in Canada. Data for patient sex; age at the time of diagnosis; and reporting province, city, and forward sortation area (fsa, the first three characters of a postal code) were analyzed. Results During 1992-2010, 1420 patients with bl in Canada were identified (incidence rate: 2.40 cases per million patient-years), of which 71.1% were male patients. Mean age at diagnosis was 55.5 ± 20.8 years. A bimodal incidence by age distribution was seen in both sexes, with pediatric- and adult-onset peaks. An analysis based on fsas identified select communities with statistically higher rates of adult bl. Several of those fsas were located within the 3 major metropolitan areas (Montreal, Vancouver, Toronto) and within self-identified lgbtq communities. The fsas with a higher socioeconomic status score were associated with lower rates of bl. Conclusions Current results highlight the geographic and historic pattern of bl in Canada. The human immunodeficiency virus remains an important risk factor for adult bl. [ABSTRACT FROM AUTHOR]

A tubular disk-and-ring, tapered accelerating structure for small electron linacs and MicroLinacs is considered. It consists of metal and dielectric elements inserted into a metallic tube to eliminate multi-cell, multi-step brazing. The structure enables a wide range of phase velocities (including non-relativistic), a wide bandwidth allowing large number of cells (for standing wave mode) or short filling time (for traveling wave mode), combination of compensated and purely π-mode cells, alternative periodic focusing built-in to the RF structure (the disks), and combining of RF and vacuum windows. RF and accelerating performance of such a long structure having up to four dozens cells is analyzed. Some of beam dynamics, thermal, and vacuum aspects of the structure and MicroLinac performance are considered as well. [ABSTRACT FROM AUTHOR]

Addition of bis(pentafluorophenyl)phosphinous acid to α,β-alkenones and α,β,β'-alkene-diones in anhydrous EtO (the solvent, in which the P-OH tautomeric form predominates) proceeds rapidly and regiospecifically at the C=C bond of the substrate at room temperature in the absence of catalysts. The reaction leads to bis(pentafluorophenyl)phosphorylated alkanones and alkanediones, as a rule, in the yields close to quantitative and can be considered as a highly efficient method for the synthesis of the corresponding functionalized phosphine oxides. The structures of obtained compounds were established by IR and NMR spectroscopy and X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

The 40-MeV electron linear accelerator RELUS-6 with a 100-mA pulse current has been designed. The standing wave accelerator with a biperiodic accelerating structure is composed of four sections and is powered from two 6-MW pulse klystrons. The operating frequency is 2856 MHz. The total length of the accelerating structure is 2.73 m. Calculations have been performed with the aim of selecting the lengths of the first three cells in the first accelerating section and the values of the accelerating field in them, so that the width of the energy spectrum at the end of the accelerator is 2%. The geometry of the accelerating structure and the power input cells has been designed. Four accelerating structures have been manufactured based on the simulation results. The structures have been tuned to the operating frequency, the predetermined accelerating field distribution, and a fixed coupling between the feed waveguide and the accelerating section. [ABSTRACT FROM AUTHOR]

The temperature distribution in the accelerating structures of standing-wave and traveling-wave electron linacs is calculated. The objects of consideration in the former and latter cases are, respectively, a circular iris waveguide with magnetic coupling and a biperiodic accelerating structure. Calculation data for steady and transient heating conditions are presented. The variation of the cell's geometry and resonance frequency with the temperature of the structure is also calculated. Calculations are made for copper structures with allowance for microwave wall losses. [ABSTRACT FROM AUTHOR]

Products of additive cyclization with ring closure at the nitrogen atom of the thiohetaryl unit were synthesized by the interaction of 4,6-dimethylpyrimidine-2-, 3-cyano-4,6-dimethylpyridine-2-, quinoline-8-, and 1,3-benzothiazole-2-sulfenyl chlorides with 3,3-dimethyl-1-butene. [ABSTRACT FROM AUTHOR]

Background: Romania was an endemic malaria country with as many as 300,000 new cases yearly and the eradication was completed in 1962. The permanent risk of malaria re-emergence in Romania maintains because of the simultaneous presence of the Anopheles maculipennis group vector species and imported malaria cases. The risk increased in the present conditions of climatic and other environmental changes. Methods & Materials: The analysis of the historical and present data regarding the presence, abundance and distribution of different vector species in Romania in correlation with the environmental, social and economic conditions led to the evaluation of the risk evolution of malaria re-appearance and the main factors involved. The entomological data were integrated with earth observation data obtained by spatial technologies and mapped to put in evidence the stratification of the present risk areas of malaria re-emergence. Results: The general level of malaria re-emergence risk varied in Romania. The risk was low after eradication linked to the low densities of vector populations because of the climatic conditions maintained in usual limits and intensive agriculture on large uniform areas. The risk gradually increased after 1990 linked to the high abundance of vector populations as before malaria eradication because of the global climate change and the land use change in Romania leading to the fragmentation of the habitat in the agricultural areas produced by the resuming to the traditional work on small private pieces of land. The present risk areas of malaria re-emergence are mapped. They generally overlap the former malaria stratification areas in Romania in accordance to the distribution of different vector species in the landscape. The new aspects are linked to the present environmental changes. Anopheles atroparvus, the main vector in Romania, has higher abundant populations and its distribution extended over all the risk areas. Anopheles daciae, possible malaria vector, has an extended distribution and higher densities than Anopheles messeae everywhere. Conclusion: The malaria re-emergence risk maintains in Romania in conditions of the climate and other environmental changes. There is the need of the permanent surveillance of the factors influencing this risk to prevent and control malaria re-appearance. [ABSTRACT FROM AUTHOR]