![129405-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/129405-Thumbnail%20Image.png?versionId=3m0LbJGYo8oaQPnTcs74YiActTYBED7f&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240619/us-west-2/s3/aws4_request&X-Amz-Date=20240619T185044Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=73c14735cdc9d6eed865b8ec844140c259c26b57352dc58796b817f926de3c12&itok=RUJnrWwP)
The Dawn Framing Camera (FC) has imaged the northern hemisphere of the Asteroid (4) Vesta at high spatial resolution and coverage. This study represents the first investigation of the overall geology of the northern hemisphere (22–90°N, quadrangles Av-1, 2, 3, 4 and 5) using these unique Dawn mission observations. We have compiled a morphologic map and performed crater size–frequency distribution (CSFD) measurements to date the geologic units. The hemisphere is characterized by a heavily cratered surface with a few highly subdued basins up to ∼200 km in diameter. The most widespread unit is a plateau (cratered highland unit), similar to, although of lower elevation than the equatorial Vestalia Terra plateau. Large-scale troughs and ridges have regionally affected the surface. Between ∼180°E and ∼270°E, these tectonic features are well developed and related to the south pole Veneneia impact (Saturnalia Fossae trough unit), elsewhere on the hemisphere they are rare and subdued (Saturnalia Fossae cratered unit). In these pre-Rheasilvia units we observed an unexpectedly high frequency of impact craters up to ∼10 km in diameter, whose formation could in part be related to the Rheasilvia basin-forming event. The Rheasilvia impact has potentially affected the northern hemisphere also with S–N small-scale lineations, but without covering it with an ejecta blanket. Post-Rheasilvia impact craters are small (<60 km in diameter) and show a wide range of degradation states due to impact gardening and mass wasting processes. Where fresh, they display an ejecta blanket, bright rays and slope movements on walls. In places, crater rims have dark material ejecta and some crater floors are covered by ponded material interpreted as impact melt.
![128354-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/128354-Thumbnail%20Image.png?versionId=FCvdYqLjWLIEq3dBmY0nVyPkGaK6GsX3&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240618/us-west-2/s3/aws4_request&X-Amz-Date=20240618T225949Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=752c0a6ca257b00358789ce07cd28a463433e1a2c0ebcd3aa72d84fc707bbc76&itok=tznLVPlU)
This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. Aerosolized Omono River virus particles of ∼40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles. The results point to a wider than expected size distribution (from ∼35 to ∼300 nm in diameter). This is likely to be owing to nonvolatile contaminants from larger droplets during aerosolization and droplet evaporation. The results suggest that the concentration of nonvolatile contaminants and the ratio between the volumes of the initial droplet and the sample particles is critical in such studies. The maximum beam intensity in the focus was found to be 1.9 × 1012 photons per µm2 per pulse. The full-width of the focus at half-maximum was estimated to be 500 nm (assuming 20% beamline transmission), and this width is larger than expected. Under these conditions, the diffraction signal from a sample-sized particle remained above the average background to a resolution of 4.25 nm. The results suggest that reducing the size of the initial droplets during aerosolization is necessary to bring small particles into the scope of detailed structural studies with X-ray lasers.
![130274-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/130274-Thumbnail%20Image.png?versionId=y2otTFmNxVfGdNlboOFY5tZyqTmTOPne&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240618/us-west-2/s3/aws4_request&X-Amz-Date=20240618T134302Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=8d6b60e768cfa8da9ac6138c9d2ccc3e8d3be65f9b7894c5e66ebfd2e0737b3b&itok=3GiCMrZE)
![130284-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/130284-Thumbnail%20Image.png?versionId=RL18_PeDsi0QZ7ifKxgMiJEVL3i4mc.x&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240606/us-west-2/s3/aws4_request&X-Amz-Date=20240606T054759Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=f3d6b15d8c73c0cf7d6967a573a9bcefad0d52398c294984b06db431689cb0d5&itok=MkSjOHVT)
![130301-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/130301-Thumbnail%20Image.png?versionId=xqj1fyeOr9I9fWJmok_xApUZSi.vLJWr&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240618/us-west-2/s3/aws4_request&X-Amz-Date=20240618T012352Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=09846605a3e524afb4977a655c57fe81fb5854b12d7f3f89f3c5e18aadb98195&itok=_EM0ee44)
![130302-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/130302-Thumbnail%20Image.png?versionId=bRVeSoMNtjtOc8xFDxSUq67rlfgCYFH1&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240605/us-west-2/s3/aws4_request&X-Amz-Date=20240605T205427Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=5397aef26823e23c5d1b8a9b8546cb83c5d889ac489d568fdbe3d29d6b0d301f&itok=yeSP2o7w)
![130306-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/130306-Thumbnail%20Image.png?versionId=v631S8PiiTl8DPeW3_O4fQhoei2bVdDu&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240619/us-west-2/s3/aws4_request&X-Amz-Date=20240619T020632Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=aa602f62f3fca9c4e7cfe797e2a731f82293df7ff121bf5233446e3c57e67a2a&itok=oFxZCiJK)
![130270-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/130270-Thumbnail%20Image.png?versionId=YWNgEwZ2.97XEslTr4xNKmSmiQp_YE6y&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240618/us-west-2/s3/aws4_request&X-Amz-Date=20240618T201535Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=b0175d358c761391d27c89044344abf1da737218cb9446c3d9fba7a9548e2d0e&itok=YfTLZqld)
![127809-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/127809-Thumbnail%20Image.png?versionId=zIVMxkgMSNfW3vpIiuNnUW9U5qWDmqPM&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240618/us-west-2/s3/aws4_request&X-Amz-Date=20240618T195746Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=a5452900e4a18e6aa6cb6a2ff640dcf85cd31d15ae280df6defa4f310b0932d6&itok=oWqhWnvz)
There is a need for indicators of transportation-land use system quality that are understandable to a wide range of stakeholders, and which can provide immediate feedback on the quality of interactively designed scenarios. Location-based accessibility indicators are promising candidates, but indicator values can vary strongly depending on time of day and transfer wait times. Capturing this variation increases complexity, slowing down calculations. We present new methods for rapid yet rigorous computation of accessibility metrics, allowing immediate feedback during early-stage transit planning, while being rigorous enough for final analyses. Our approach is statistical, characterizing the uncertainty and variability in accessibility metrics due to differences in departure time and headway-based scenario specification. The analysis is carried out on a detailed multi-modal network model including both public transportation and streets. Land use data are represented at high resolution. These methods have been implemented as open-source software running on commodity cloud infrastructure. Networks are constructed from standard open data sources, and scenarios are built in a map-based web interface. We conclude with a case study, describing how these methods were applied in a long-term transportation planning process for metropolitan Amsterdam.
![127817-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-04/127817-Thumbnail%20Image.png?versionId=F77E_mxkT0dciKjM4mitz94NjJcISRtG&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240617/us-west-2/s3/aws4_request&X-Amz-Date=20240617T180537Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=d0129a805c66d09f259eab32c17e3cedb9c1c0522b9a5f73619d1c7041abfc36&itok=cJmu7_Mx)
Accessibility is increasingly used as a metric when evaluating changes to public transport systems. Transit travel times contain variation depending on when one departs relative to when a transit vehicle arrives, and how well transfers are coordinated given a particular timetable. In addition, there is necessarily uncertainty in the value of the accessibility metric during sketch planning processes, due to scenarios which are underspecified because detailed schedule information is not yet available. This article presents a method to extend the concept of "reliable" accessibility to transit to address the first issue, and create confidence intervals and hypothesis tests to address the second.