Determination of longitudinal bunch shape by means of coherent Smith-Purcell radiation

Coherent enhancement of the Smith-Purcell radiation produced from the interaction of a 1.8 MeV electron beam with a grating has been observed. The emitted radiation has been measured at angles in the 40° to 120° range, which correspond to wavelengths from 0.65 to 4 mm, approximately. The radiated power was 320 mW at 90°. Its angular distribution agrees well with the description of the process in terms of induced surface currents and has been used to infer the longitudinal profile of the electron bunch. It is concluded that the bunch has an approximately triangular profile, with 85% of the bunch particles contained within 14 ps. The possibilities of the technique as a bunch-shape diagnostic tool are also discussed. © 2002 The American Physical Society

Determination of longitudinal bunch shape by means of coherent Smith-Purcell radiation

Coherent enhancement of the Smith-Purcell radiation produced from the interaction of a 1.8 MeV electron beam with a grating has been observed. The emitted radiation has been measured at angles in the 40° to 120° range, which correspond to wavelengths from 0.65 to 4 mm, approximately. The radiated power was 320 mW at 90°. Its angular distribution agrees well with the description of the process in terms of induced surface currents and has been used to infer the longitudinal profile of the electron bunch. It is concluded that the bunch has an approximately triangular profile, with 85% of the bunch particles contained within 14 ps. The possibilities of the technique as a bunch-shape diagnostic tool are also discussed

Rotational cooling of heteronuclear molecular ions with ^1-Sigma, ^2-Sigma, ^3-Sigma and ^2-Pi electronic ground states

The translational motion of molecular ions can be effectively cooled sympathetically to translational temperatures below 100 mK in ion traps through Coulomb interactions with laser-cooled atomic ions. The ro-vibrational degrees of freedom, however, are expected to be largely unaffected during translational cooling. We have previously proposed schemes for cooling of the internal degrees of freedom of such translationally cold but internally hot heteronuclear diatomic ions in the simplest case of ^1-Sigma electronic ground state molecules. Here we present a significant simplification of these schemes and make a generalization to the most frequently encountered electronic ground states of heteronuclear molecular ions: ^1-Sigma, ^2-Sigma, ^3-Sigma and ^2-Pi. The schemes are relying on one or two laser driven transitions with the possible inclusion of a tailored incoherent far infrared radiation field.Comment: 16 pages, 13 figure

Terahertz Techniques

Research and development in the terahertz portion of the electromagnetic spectrum has expanded very rapidly during the past fifteen years due to major advances in sources, detectors and instrumentation. Many scientists and engineers are entering the field and this volume offers a comprehensive and integrated treatment of all aspects of terahertz technology. The three authors, who have been active researchers in this region over a number of years, have designed Terahertz Techniques to be both a general introduction to the subject and a definitive reference resource for all those involved in this exciting research area

Efficacy Of The Quadrivalent HPV Vaccine In Cervical Cancer Prevention Strategy In The Gambia

Background and Objective: Persistent infection with high risk Human Papillomavirus (HR HPV) genotype causes 80% of cervical cancers. HR HPV 16 and 18 are responsible for 70% of cervical cancer cases, worldwide. Three prophylactic HPV vaccines have been developed to prevent HPV infections. In the Gambia, cervical cancer is the most frequent diagnosed cancer representing approximately 30% of all female cancers. The quadrivalent HPV vaccine, which targets genotypes 16,18, 6 and 11 was recently piloted in the West Coast Region where majority of cervical cancer cases were reported. In order to evaluate the potential efficacy of the quadrivalent vaccine, this study assessed regional genotype distribution to ensure the HPV vaccine prevention strategy would be effective in this population. Methods: 232 endocervical samples were collected from women age 20-49 years old residing in Banjul and West Coast Region. DNA was isolated using the QIAamp DNA Mini Kit (Qiagen). HPV detection was carried out by PCR amplification using primer sets PGMY09/11, which targets the (L1) Major capsid gene of the virus. Genotyping was performed by Sanger sequencing technique. Results: nine different HR- HPV genotypes were identified. HPV 52 (31%) was the most prevalent HR genotype, followed by 51, 58 and 66(each12.5%). HPV 16 accounts for 6% of the HR-HPV and was the eighth of all HPV genotype identified. HR- HPV 18 was not detected in any of the samples. HR-HPV distribution was higher in the 26-30 age group.HPV 61 was the most common low risk genotype isolated. Sequence analysis showed all HR genotypes detected were not homologous to African isolates but isolates that originated from America, Europe and Asia. Conclusion: The success of a cervical cancer vaccine prevention strategy should consider the dominant circulating HR HPV type. In the Gambia, the vaccine currently available may be of limited value if the other HR-HPV types are responsible for cytological abnormalities in these women

A Preliminary Report: Cervical Human Papilloma Virus Genotype Distribution in Reproductive Aged Women Attending Primary Health Care in Urban Gambia

Persistent infection with high risk genotypes of Human Papilloma Virus (HPV) plays a vital role in the development of most cervical cancers and Cervical Intraepithelial Neoplasia (CIN) among sexually active women worldwide. In the Gambia, cervical cancer is the most frequently diagnosed cancer amongst Gambian women representing about 30% of all registered female cancers. The bivalent HPV vaccine, which targets HPV genotypes 16 and 18, was introduced in urban Gambia in 2014. The aim of this study was to determine HPV genotype distribution and the risk factors associated with HPV infections in the urban population and to determine the efficacy of the bivalent vaccine in this population. Sexually active reproductive women (N= 178; 20 - 49 years old) attending a polyclinic were enrolled in the study. A designed questionnaire was administered to capture socio-demographic and behavioural risk factors of study participants. Endocervical and high vaginal swabs were collected to determine HPV genotype distribution and co-infection with other genital STI pathogens. HPV and sample adequacy was determined using the consensus primers PGMY09/11 targeting the late protein (L1) gene and the Histocompatibility leucocyte antigen (HLA) housekeeping gene. HPV genotyping was performed by DNA sequencing on positive HPV samples. Genital STI pathogens were identified by Microbiological analysis and Molecular detection. HPV infection rate was 12.4% and was most prevalence in women between the ages of 31 -39 years old. Overall, 22 HPV genotypes were detected and the most prevalent high risk genotype was HPV 52. About 60% of participants infected with HPV were co-infected with Ureaplasma urealyticum. Bivariate analysis shows that infection with Ureaplasma urealyticum, early sexual debut, Low level of education, female circumcision and having >3 life time sexual partners were all risk factors for HPV infection but not associated significantly with HPV (p > 0.05). This study is the first study carried out in urban Gambia and has demonstrated that the bivalent vaccine might not be adequate to protect this population from HPV infection as most high risk genotypes identified in this study are not targeted by the bivalent vaccine