Momentum space tomographic imaging of photoelectrons

We apply tomography, a general method for reconstructing 3-D distributions from multiple projections, to reconstruct the momentum distribution of electrons produced via strong field photoionization. The projections are obtained by rotating the electron distribution via the polarization of the ionizing laser beam and recording a momentum spectrum at each angle with a 2-D velocity map imaging spectrometer. For linearly polarized light the tomographic reconstruction agrees with the distribution obtained using an Abel inversion. Electron tomography, which can be applied to any polarization, will simplify the technology of electron imaging. The method can be directly generalized to other charged particles.Comment: Accepted by J. Phys.

Alignment dependent enhancement of the photo-electron cutoff for multi-photon ionization of molecules

The multiphoton ionization rate of molecules depends on the alignment of the molecular axis with respect to the ionizing laser polarization. By studying molecular frame photo-electron angular distributions from N$_2$, O$_2$ and benzene, we illustrate how the angle-dependent ionization rate affects the photo-electron cutoff energy. We find alignment can enhance the high energy cutoff of the photo-electron spectrum when probing along a nodal plane or when ionization is otherwise suppressed. This is supported by calculations using a tunneling model with a single ion state.Comment: 4 pages, 4 figure

Effect of light polarization on plasma distribution and filament formation

We show that, for 200 fs light pulses at 790 nm, the formation of filaments is strongly affected by the laser light polarization . Filamentation does not exist for a pure circularly polarized light, propagating in vacuum before focusing in air, while there is no difference for focusing the light in air or vacuum for linearly polarized light.Comment: 4pages 2 figure

Partitioning of the linear photon momentum in multiphoton ionization

The balance of the linear photon momentum in multiphoton ionization is studied experimentally. In the experiment argon and neon atoms are singly ionized by circularly polarized laser pulses with a wavelength of 800 nm and 1400 nm in the intensity range of 10^{14} - 10^{15} W/cm^2. The photoelectrons are measured using velocity map imaging. We find that the photoelectrons carry linear momentum corresponding to the photons absorbed above the field free ionization threshold. Our finding has implications for concurrent models of the generation of terahertz radiation in filaments.Comment: 4 pages, 3 figure

Non-excisional techniques for the treatment of intergluteal pilonidal sinus disease:a systematic review

Non-excisional techniques for pilonidal sinus disease (PSD) have gained popularity over the last years. The aim of this study was to review short and long-term outcomes for non-excisional techniques with special focus on the additive effect of treatment of the inner lining of the sinus cavity and the difference between primary and recurrent PSD. A systematic search was conducted in Embase, Medline, Web of Science Core Collection, Cochrane and Google Scholar databases for studies on non-excisional techniques for PSD including pit picking techniques with or without additional laser or phenol treatment, unroofing, endoscopic techniques and thrombin gelatin matrix application. Outcomes were recurrence rates, healing rates, complication rates, wound healing times and time taken to return to daily activities. In total, 31 studies comprising 8100 patients were included. Non-excisional techniques had overall healing rates ranging from 67 to 100%. Recurrence rates for pit picking, unroofing and gelatin matrix application varied from 0 to 16% depending on the follow-up time. Recurrence rates after additional laser, phenol and endoscopic techniques varied from 0 to 29%. Complication rates ranged from 0 to 16%, and the wound healing time was between three and forty-seven days. The return to daily activities varied from one to nine days. Non-excisional techniques are associated with fast recovery and low morbidity but recurrence rates are high. Techniques that attempt to additionally treat the inner lining of the sinus have worse recurrence rates than pit picking alone. Recurrence rates do not differ between primary and recurrent disease.</p

Sustainable Agriculture for Alaska and the Circumpolar North: Part III. Meeting the Challenges of High-Latitude Farming

Agriculture is a severely underdeveloped industry in Alaska and throughout most of the Subarctic. Growers and entrepreneurs must overcome a diverse set of challenges to achieve greater sustainability in northern communities where resilience is threatened by food insecurity and challenges to northern agriculture have limited the industry. However, several field-based or social policy solutions to problems of high-latitude agriculture have been proposed or are being put into practice. Field-based solutions include the use of special infrastructure or farm management strategies to extend the short growing season, improve soil quality, integrate appropriate pest and irrigation management practices, and further develop the livestock sector. Social and policy solutions are resolutions or decisions reached by stakeholders and government, often through cooperative interaction and discussion. These solutions stem from meaningful discussion and decision making among community members, organizations, agencies, and legislators. Social and policy solutions for Alaska include addressing the high costs of land and the preservation of agricultural lands; improved markets and market strategies; more appropriate funding for research, education and infrastructure; and other integrative or cooperative efforts. Collectively, these solutions will work to improve the outlook for sustainable agriculture in Alaska.En Alaska et dans une grande partie des régions subarctiques, l’agriculture est une industrie extrêmement sous-développée. Les producteurs et les entrepreneurs doivent surmonter un ensemble de défis variés pour donner lieu à une plus grande durabilité dans les collectivités nordiques, là où la résilience est menacée par l’insécurité alimentaire et où les défis caractérisant l’agriculture nordique imposent des restrictions à l’industrie. Cependant, plusieurs solutions apportées sur le terrain ou par le biais de politiques sociales vis-à-vis des problèmes touchant l’agriculture en haute latitude ont été proposées ou sont en train d’être mises en pratique. Parmi les solutions apportées sur le terrain, notons le recours à une infrastructure particulière ou à des stratégies de gestion agricole visant à prolonger la courte saison de croissance, à améliorer la qualité du sol, à intégrer des méthodes de gestion de l’irrigation et des organismes nuisibles, et à mettre davantage l’accent sur le secteur de l’élevage du bétail. Les solutions en matière de politiques sociales prennent la forme de résolutions ou de décisions prises par les parties prenantes et le gouvernement, souvent en collaboration et à la lumière de discussions. Ces solutions découlent de discussions et de prises de décisions importantes entre les membres des collectivités, les organisations, les agences et les législateurs. Les solutions de politiques sociales de l’Alaska portent notamment sur le coût élevé de la terre et la conservation des terres agricoles, sur l’amélioration des marchés et des stratégies de commercialisation, sur la nécessité d’obtenir des sources de financement plus adéquates pour la recherche, l’éducation et l’infrastructure, ainsi que sur d’autres efforts d’intégration et de coopération. Ensemble, ces solutions permettront d’améliorer la conjoncture de l’agriculture durable en Alaska

Sustainable Agriculture for Alaska and the Circumpolar North: Part II. Environmental, Geophysical, Biological and Socioeconomic Challenges

Local agriculture, food security and food supply are limited in Alaska, as well as in much of the circumpolar North. These limitations stem from a suite of challenges that have never been well characterized, categorized, or wholly defined. We identify these challenges as being environmental, geophysical, biological, or socioeconomic in nature, noting that some challenges are interrelated. Additionally, Alaska is expansive, and growing conditions are highly variable across different regions and microclimates of the state. Environmental challenges to Alaskan agriculture are generally linked to high latitude and include strong seasonality, a short growing season, cold temperatures, and unpredictable frosts. Geophysical challenges are characterized by a high percentage of soils that are wet and cold or low in natural fertility. Biological challenges include cultivar adaptability and selection; the control of various pests, weeds, and diseases; and decreased microbial activity in cold soils, which can allow pesticides to linger and slow mineralization of organic fertilizers. Socioeconomic challenges to farming in Alaska are especially limiting and may categorically represent the strongest hindrances to agriculture. They often overlap or interact with many of the identified agro-ecological and biogeographic challenges. Major socioeconomic issues can be a relatively low financial incentive or reward for farmers; inconsistent or limited markets; the high cost of land, infrastructure, and inputs; zoning challenges; a lack of cooperatives; and for rural farmers, time conflicts with more traditional means of subsistence food acquisition. These challenges collectively represent factors that limit agriculture in Alaska, and they provide a basis and justification for developing more sustainable solutions. agriculture; Alaska; challenges; climate; circumpolar; farming; soils; subarctic; sustainable; socioeconomicEn Alaska, l’agriculture locale, la sécurité alimentaire et les approvisionnements en vivres sont limités. C’est également le cas d’une grande partie du Nord circumpolaire. Ces limitations découlent d’un ensemble de défis qui n’ont jamais été bien caractérisés, catégorisés ou entièrement définis. Nous estimons que ces défis sont d’ordre environnemental, géophysique, biologique ou socioéconomique, et que certains des défis sont interreliés. De plus, l’Alaska est d’une grande étendue, et les conditions de croissance varient énormément d’une région à l’autre et d’un microclimat à l’autre de l’État. De manière générale, les défis environnementaux inhérents à l’agriculture alaskienne ont trait à la haute latitude, ce qui comprend une importante saisonnalité, une courte saison de croissance, des températures froides et des gelées imprévisibles. Pour leur part, les défis géophysiques sont caractérisés par un fort pourcentage de sols humides et froids, ou encore, de sols dont la fertilité naturelle est faible, puis les défis d’ordre biologique ont trait à l’adaptabilité et à la sélection des cultivars, à la lutte contre divers organismes nuisibles, les mauvaises herbes et les maladies, ainsi qu’à une activité microbienne réduite dans les sols froids, ce qui permet aux pesticides de rester plus longtemps et ralentit la minéralisation des engrais organiques. Quant aux défis de nature socioéconomique, ils imposent des restrictions particulièrement fortes en Alaska, au point où ils pourraient même catégoriquement représenter le plus grand obstacle à l’agriculture. Dans bien des cas, les défis se chevauchent ou ont une action réciproque sur un grand nombre d’enjeux agroécologiques et biogéographiques. De plus, les grands enjeux socioéconomiques peuvent prendre la forme de récompenses financières relativement faibles pour les agriculteurs, de marchés irréguliers ou limités, du coût élevé de la terre, des infrastructures et des intrants, d’obstacles inhérents au zonage, d’un manqué de coopératives et, dans le cas des agriculteurs ruraux, de conflits d’emploi du temps avec les moyens de subsistance plus traditionnels d’acquisition de la nourriture. Collectivement, ces défis représentent les facteurs qui imposent des restrictions à l’agriculture en Alaska, et ils constituent les fondements et la justification nécessaires au développement de solutions plus durables

Controlled Assembly of Macromolecular β-Sheet Fibrils

Construction of functional molecular devices by directed assembly processes is one of the main challenges in the field of nanotechnology. Many approaches to this challenge use biological assembly as a source of inspiration for the build up of new materials with controlled organization at the nanoscale. In particular, the self-assembly properties of β-sheet peptides have been used in the design of supramolecular materials, such as tapes, nanotubes, and fibrils

Laparoscopic subtotal hysterectomy versus laparoscopic total hysterectomy: a decade of experience

At present, there are only few data on the surgical outcomes of laparoscopic hysterectomy (LH). Up till now, it has been unclear whether there is a difference in number of complications among the subcategories of laparoscopic total hysterectomy and laparoscopic subtotal hysterectomy (LSH). Therefore, we have performed a retrospective analysis to evaluate the peri- and postoperative outcomes in women undergoing LSH versus LH. This multi-centre retrospective cohort study (Canadian Task Force classification II-2) was conducted in multi-centres (two teaching hospitals and one university medical centre) in the Netherlands, all experienced in minimally invasive gynaecology. In a multi-centre retrospective cohort study we compared the long-term outcomes of laparoscopic subtotal hysterectomy and laparoscopic total hysterectomy (including laparoscopic assisted vaginal hysterectomy, laparoscopic hysterectomy and total laparoscopic hysterectomy). All laparoscopic hysterectomies from the last 10 years (January 1998 till December 2007) were included. Patient characteristics, intra- and postoperative complications, operating time and duration of hospital stay were recorded. The minimum follow-up was 6 months. A total of 390 cases of laparoscopic hysterectomies were included in the analysis: 192 laparoscopic subtotal hysterectomies and 198 laparoscopic total hysterectomies. Patient characteristics such as age and parity were equal in the groups. The overall number of short-term and long-term complications was comparable in both groups: 17% and 15%. Short-term complications (bleeding, fever) were 3% in the LSH group and 12% in the LH group. Long-term complications were (tubal prolapse and cervical stump reoperations) 15% in the LSH group and 3% in the LH group. Laparoscopic subtotal hysterectomy as compared with the different types of laparoscopic total hysterectomy is associated with more long-term postoperative complications, whereas laparoscopic total hysterectomy is associated with more short-term complications

A new instrument to measure high value, cost-conscious care attitudes among healthcare stakeholders: Development of the MHAQ

Background: Residents have to learn to provide high value, cost-conscious care (HVCCC) to counter the trend of excessive healthcare costs. Their learning is impacted by individuals from different stakeholder groups within the workplace environment. These individuals' attitudes toward HVCCC may influence how and what residents learn. This study was carried out to develop an instrument to reliably measure HVCCC attitudes among residents, staff physicians, administrators, and patients. The instrument can be used to assess the residency-training environment. Method: The Maastricht HVCCC Attitude Questionnaire (MHAQ) was developed in four phases. First, we conducted exploratory factor analyses using original data from a previously published survey. Next, we added nine items to strengthen subscales and tested the new questionnaire among the four stakeholder groups. We used exploratory factor analysis and Cronbach's alphas to define subscales, after which the final version of the MHAQ was constructed. Finally, we used generalizability theory to determine the number of respondents (residents or staff physicians) needed to reliably measure a specialty attitude score. Results: Initial factor analysis identified three subscales. Thereafter, 301 residents, 297 staff physicians, 53 administrators and 792 patients completed the new questionnaire between June 2017 and July 2018. The best fitting subscale composition was a three-factor model. Subscales were defined as high-value care, cost incorporation, and perceived drawbacks. Cronbach's alphas were between 0.61 and 0.82 for all stakeholders on all subscales. Sufficient reliability for assessing national specialty attitude (G-coefficient > 0.6) could be achieved from 14 respondents. Conclusions: The MHAQ reliably measures individual attitudes toward HVCCC in different stakeholders in health care contexts. It addresses key dimensions of HVCCC, providing content validity evidence. The MHAQ can be used to identify frontrunners of HVCCC, pinpoint aspects of residency training that need improvement, and benchmark and compare across specialties, hospitals and regions