Nanofluidic and monolithic environmental cells for cryogenic microscopy.

We present a device capable of combining nanofluidics and cryogenic transmission electron microscopy (cryo-TEM) to allow inspection of water-soluble samples under near-native conditions. The devices can be produced in a multitude of designs, but as a general rule, they consist of channels or chambers enclosed between two electron-transparent silicon nitride windows. With the appropriate design, those devices can allow screening of multiple samples in parallel and remove the interaction between the sample and the environment (no air-water interface). We demonstrate channel sizes from 80 to 500 nm in height and widths from 100 to 2000 µm. The presented fabrication flow allows producing hollow devices on a single wafer eliminating the need of aligning or bonding two half-cavities from separate wafers, which provides additional resistance to thermal stress. Taking advantage of a single-step through-membrane exposure with a 100 keV electron beam, we introduced arrays of thin (10-15 nm) electron-transparent silicon nitride membrane windows aligned between top and bottom (200-250 nm) carrier membranes. Importantly, the final devices are compatible with standard TEM holders. Furthermore, they are compatible with rapid freezing of samples, which is crucial for the formation of vitreous water, hence avoiding the formation of crystalline ice, that is detrimental for TEM imaging. To demonstrate the potential of this technology, we tested those devices in imaging experiments verifying their applicability for cryo-TEM applications and proved that vitreous water could be prepared through conventional plunge freezing of the chips.

Micrometre resolution of a charge integrating microstrip detector with single photon sensitivity.

A synchrotron beam has been used to test the spatial resolution of a single-photon-resolving integrating readout-chip coupled to a 320 µm-thick silicon strip sensor with a dedicated readout system. Charge interpolation methods have yielded a spatial resolution of σ(x) ≃ 1.8 µm for a 20 µm-pitch strip.

Beam-induced damage on diffractive hard X-ray optics.

The issue of beam-induced damage on diffractive hard X-ray optics is addressed. For this purpose a systematic study on the radiation damage induced by a high-power X-ray beam is carried out in both ambient and inert atmospheres. Diffraction gratings fabricated by three different techniques are considered: electroplated Au gratings both with and without the polymer mold, and Ir-coated Si gratings. The beam-induced damage is monitored by X-ray diffraction and evaluated using scanning electron microscopy.

Author Correction: Nanofocusing of hard X-ray free electron laser pulses using diamond based Fresnel zone plates.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Paleoclimatic signature in terrestrial flood deposits.

Large-scale process simulation was used to reconstruct the geologic evolution during the past 600,000 years of an alluvial fan in northern California. In order to reproduce the sedimentary record, the simulation accounted for the dynamics of river flooding, sedimentation, subsidence, land movement that resulted from faulting, and sea level changes. Paleoclimatic trends induced fluctuations in stream flows and dominated the development of the sedimentary deposits. The process simulation approach serves as a quantitative means to explore the genesis of sedimentary architecture and its link to past climatic conditions and fault motion.

Two-dimensional structure from random multiparticle X-ray scattering images using cross-correlations.

Knowledge of the structure of biological macromolecules, especially in their native environment, is crucial because of the close structure-function relationship. X-ray small-angle scattering is used to determine the shape of particles in solution, but the achievable resolution is limited owing to averaging over particle orientations. In 1977, Kam proposed to obtain additional structural information from the cross-correlation of the scattering intensities. Here we develop the method in two dimensions, and give a procedure by which the single-particle diffraction pattern is extracted in a model-independent way from the correlations. We demonstrate its application to a large set of synchrotron X-ray scattering images on ensembles of identical, randomly oriented particles of 350 or 200 nm in size. The obtained 15 nm resolution in the reconstructed shape is independent of the number of scatterers. The results are discussed in view of proposed 'snapshot' scattering by molecules in the liquid phase at X-ray free-electron lasers.

Nanofocusing of hard X-ray free electron laser pulses using diamond based Fresnel zone plates.

A growing number of X-ray sources based on the free-electron laser (XFEL) principle are presently under construction or have recently started operation. The intense, ultrashort pulses of these sources will enable new insights in many different fields of science. A key problem is to provide x-ray optical elements capable of collecting the largest possible fraction of the radiation and to focus into the smallest possible focus. As a key step towards this goal, we demonstrate here the first nanofocusing of hard XFEL pulses. We developed diamond based Fresnel zone plates capable of withstanding the full beam of the world's most powerful x-ray laser. Using an imprint technique, we measured the focal spot size, which was limited to 320 nm FWHM by the spectral band width of the source. A peak power density in the focal spot of 4×10(17)W/cm(2) was obtained at 70 fs pulse length.

Outcome of AIDS-associated cytomegalovirus colitis in the era of potent antiretroviral therapy.

The effect of protease inhibitors (PIs) on the outcome of AIDS-associated cytomegalovirus (CMV) colitis is unknown. The aim of this study was to determine the impact of PIs on the recurrence of CMV disease and long-term survival in a large cohort of acquired immunodeficiency syndrome (AIDS) patients with CMV colitis. We reviewed the medical records of 252 AIDS patients who were diagnosed with CMV colitis by colonoscopy between January 1992 and January 1997 at Bellevue Hospital (New York, NY, U.S.A.). Follow-up data were obtained from chart review and direct telephone contact. A complete response to ganciclovir and/or foscarnet therapy was seen in 87.0% of the patients. Recurrence of CMV colitis occurred in 53.1% of patients and was significantly less common in those who received maintenance therapy (36.1% vs. 56.7%; p = 0.03) and in those who were treated with PIs (22.8% vs. 71.9%; p < 0.001). During follow-up. 69.3% of patients died. Multivariate analysis using Cox regression showed that mortality was increased in patients with recurrent CMV colitis (relative risk [RR] of death, 1.7: 95% CI, 1.1-2.6; p = 0.02) and comorbid disease (RR, 1.5: 95% CI, 1.1-2.2; p = 0.02), and decreased in those who were treated with PIs (RR, 0.42; 95% CI, 0.3-0.7; p = 0.001). The median survival was 71 weeks and was significantly longer in patients who were treated with PIs than in those who did not receive these potent anti-retroviral medications (99 vs. 51 weeks; p < 0.001). PIs significantly improve the outcome of AIDS-associated CMV colitis.

A phase I and pharmacokinetic study of intraperitoneal carboplatin and etoposide.

BACKGROUND: We attempted to determine the maximum tolerated dose and toxicity of etoposide (VP-16) when administered in combination with carboplatin (CBDCA) (300 mg m-2) and administered via the intraperitoneal (IP) route. METHODS AND MATERIALS: A total of 26 patients were treated on this trial. CBDCA was administered at a fixed dose of 300 mg m-2) while VP-16 was started at a dose of 200 mg m-2 and escalated at 50 mg m-2 increments. Both agents were mixed together in 2 litres of 5% Dextrose and administered as quickly as possible into the peritoneal cavity. Pharmacokinetic studies were performed at the maximum tolerated dose (MTD). RESULTS: The MTD for this regimen was CBDCA 300 mg m-2 and VP-16 350 mg m-2. Patients > or = 70 years of age or who had received more than six cycles of previous chemotherapy, tolerated this regimen poorly. The MTD for this group of patients was CBDCA 200 mg m-2 and VP-16 50 mg m-2. Neutropenia was the dose limiting toxicity for both groups. The mean peritoneal/plasma peak ratio was 18.3 for CBDCA and 12.7 for VP-16. The pharmacologic advantage (peritoneal/plasma AUC ratio) was 14.9 for CBDCA and 8.8 for VP-16. Although measurable disease was not a requirement for entrance into this study a response rate of 27% was noted in 15 patients with evaluable disease who had ovarian cancer. CONCLUSIONS: A pharmacologic advantage exists for both CBDCA and VP-16 when administered together via the IP route.