Characterizing the Suture Pullout Force for Human Small Bowel.

Performing a small bowel anastomosis, or reconnecting small bowel segments, remains a core competency and critical step for the successful surgical management of numerous bowel and urinary conditions. As surgical education and technology moves toward improving patient outcomes through automation and increasing training opportunities, a detailed characterization of the interventional biomechanical properties of the human bowel is important. This is especially true due to the prevalence of anastomotic leakage as a frequent (3.02%) postoperative complication of small bowel anastomoses. This study aims to characterize the forces required for a suture to tear through human small bowel (suture pullout force, SPOF), while analyzing how these forces are affected by tissue orientation, suture material, suture size, and donor demographics. 803 tests were performed on 35 human small bowel specimens. A uni-axial test frame was used to tension sutures looped through 10 × 20 mm rectangular bowel samples to tissue failure. The mean SPOF of the small bowel was 4.62±1.40 N. We found no significant effect of tissue orientation (p = 0.083), suture material (p = 0.681), suture size (p = 0.131), age (p = 0.158), sex (p = .083), or body mass index (BMI) (p = 0.100) on SPOF. To our knowledge, this is the first study reporting human small bowel SPOF. Little research has been published about procedure-specific data on human small bowel. Filling this gap in research will inform the design of more accurate human bowel synthetic models and provide an accurate baseline for training and clinical applications.

AMX - the highly automated macromolecular crystallography (17-ID-1) beamline at the NSLS-II.

The highly automated macromolecular crystallography beamline AMX/17-ID-1 is an undulator-based high-intensity (>5 × 1012 photons s-1), micro-focus (7 µm × 5 µm), low-divergence (1 mrad × 0.35 mrad) energy-tunable (5-18 keV) beamline at the NSLS-II, Brookhaven National Laboratory, Upton, NY, USA. It is one of the three life science beamlines constructed by the NIH under the ABBIX project and it shares sector 17-ID with the FMX beamline, the frontier micro-focus macromolecular crystallography beamline. AMX saw first light in March 2016 and started general user operation in February 2017. At AMX, emphasis has been placed on high throughput, high capacity, and automation to enable data collection from the most challenging projects using an intense micro-focus beam. Here, the current state and capabilities of the beamline are reported, and the different macromolecular crystallography experiments that are routinely performed at AMX/17-ID-1 as well as some plans for the near future are presented.

Ureteral Strictures Following Ureteroscopy for Kidney Stone Disease: A Population-based Assessment.

PURPOSE: As the prevalence of urolithiasis increases and ureteroscopy is used more frequently, the risks of uncommon complications such as ureteral stricture may become more notable. Our objective is to assess the rate and associated risk factors of ureteral stricture formation in patients undergoing ureteroscopy. MATERIALS AND METHODS: Utilizing the IBM MarketScan research database, we evaluated data from 2008 to 2019 and compared ureteral stricture rates and their management following ureteroscopy to subjects who had shock wave lithotripsy. Shock wave lithotripsy was used as a comparison group to represent the rate of stricture from stone disease alone. A third group of those having both shock wave lithotripsy and ureteroscopy was included. Patients and secondary procedures were identified using Current Procedural Terminology, and International Classification of Diseases-9 and -10 codes. RESULTS: A total of 329,776 patients received ureteroscopy, shock wave lithotripsy, or shock wave lithotripsy+ureteroscopy between 2008 and 2019. Stricture developed in 2.9% of patients after ureteroscopy, 1.5% after shock wave lithotripsy, and 2.6% after shock wave lithotripsy+ureteroscopy. In the multivariable model, rates of stricture were 1.7-fold higher after ureteroscopy vs shock wave lithotripsy (OR:1.71, 95% CI 1.62-1.81). Preoperative hydronephrosis, age, prior stones/intervention, and concurrent kidney and ureteral stones were associated with increased risk of stricture. Of those with strictures incurred after ureteroscopy, 35% required drainage, 21% had endoscopic intervention, 4.8% required reconstructive surgery, and 1.7% underwent nephrectomy. CONCLUSIONS: Ureteral stricture rate after ureteroscopy of nearly 3% was higher than expected and approximately twice the rate attributable to stone disease alone. Factors associated with the stone as well as instrumentation were found to be risk factors. The morbidity of stricture disease following ureteroscopy was significant.

Fragmentation of Stones by Burst Wave Lithotripsy in the First 19 Humans.

PURPOSE: We report stone comminution in the first 19 human subjects by burst wave lithotripsy (BWL), which is the transcutaneous application of focused, cyclic ultrasound pulses. MATERIALS AND METHODS: This was a prospective multi-institutional feasibility study recruiting subjects undergoing clinical ureteroscopy (URS) for at least 1 stone ≤12 mm as measured on computerized tomography. During the planned URS, either before or after ureteroscope insertion, BWL was administered with a handheld transducer, and any stone fragmentation and tissue injury were observed. Up to 3 stones per subject were targeted, each for a maximum of 10 minutes. The primary effectiveness outcome was the volume percent comminution of the stone into fragments ≤2 mm. The primary safety outcome was the independent, blinded visual scoring of tissue injury from the URS video. RESULTS: Overall, median stone comminution was 90% (IQR 20, 100) of stone volume with 21 of 23 (91%) stones fragmented. Complete fragmentation (all fragments ≤2 mm) within 10 minutes of BWL occurred in 9 of 23 stones (39%). Of the 6 least comminuted stones, likely causative factors for decreased effectiveness included stones that were larger than the BWL beamwidth, smaller than the BWL wavelength or the introduction of air bubbles from the ureteroscope. Mild reddening of the papilla and hematuria emanating from the papilla were observed ureteroscopically. CONCLUSIONS: The first study of BWL in human subjects resulted in a median of 90% comminution of the total stone volume into fragments ≤2 mm within 10 minutes of BWL exposure with only mild tissue injury.

First Series Using Ultrasonic Propulsion and Burst Wave Lithotripsy to Treat Ureteral Stones.

PURPOSE: Our goal was to test transcutaneous focused ultrasound in the form of ultrasonic propulsion and burst wave lithotripsy to reposition ureteral stones and facilitate passage in awake subjects. MATERIALS AND METHODS: Adult subjects with a diagnosed proximal or distal ureteral stone were prospectively recruited. Ultrasonic propulsion alone or with burst wave lithotripsy was administered by a handheld transducer to awake, unanesthetized subjects. Efficacy outcomes included stone motion, stone passage, and pain relief. Safety outcome was the reporting of associated anticipated or adverse events. RESULTS: Twenty-nine subjects received either ultrasonic propulsion alone (n = 16) or with burst wave lithotripsy bursts (n = 13), and stone motion was observed in 19 (66%). The stone passed in 18 (86%) of the 21 distal ureteral stone cases with at least 2 weeks follow-up in an average of 3.9±4.9 days post-procedure. Fragmentation was observed in 7 of the burst wave lithotripsy cases. All subjects tolerated the procedure with average pain scores (0-10) dropping from 2.1±2.3 to 1.6±2.0 (P = .03). Anticipated events were limited to hematuria on initial urination post-procedure and mild pain. In total, 7 subjects had associated discomfort with only 2.2% (18 of 820) propulsion bursts. CONCLUSIONS: This study supports the efficacy and safety of using ultrasonic propulsion and burst wave lithotripsy in awake subjects to reposition and break ureteral stones to relieve pain and facilitate passage.

Characterization of Puncture Forces of the Human Trachea and Cricothyroid Membrane.

Accurate human tissue biomechanical data represents a critical knowledge gap that will help facilitate the advancement of new medical devices, patient-specific predictive models, and training simulators. Tissues related to the human airway are a top priority, as airway medical procedures are common and critical. Placement of a surgical airway, though less common, is often done in an emergent (cricothyrotomy) or urgent (tracheotomy) fashion. This study is the first to report relevant puncture force data for the human cricothyroid membrane and tracheal annular ligaments. Puncture forces of the cricothyroid membrane and tracheal annular ligaments were collected from 39 and 42 excised human donor tracheas, respectively, with a mechanized load frame holding various surgical tools. The average puncture force of the cricothyroid membrane using an 11 blade scalpel was 1.01 ± 0.36 N, and the average puncture force of the tracheal annular ligaments using a 16 gauge needle was 0.98 ± 0.34 N. This data can be used to inform medical device and airway training simulator development as puncture data of these anatomies has not been previously reported.

FMX - the Frontier Microfocusing Macromolecular Crystallography Beamline at the National Synchrotron Light Source II.

Two new macromolecular crystallography (MX) beamlines at the National Synchrotron Light Source II, FMX and AMX, opened for general user operation in February 2017 [Schneider et al. (2013). J. Phys. Conf. Ser. 425, 012003; Fuchs et al. (2014). J. Phys. Conf. Ser. 493, 012021; Fuchs et al. (2016). AIP Conf. Proc. SRI2015, 1741, 030006]. FMX, the micro-focusing Frontier MX beamline in sector 17-ID-2 at NSLS-II, covers a 5-30 keV photon energy range and delivers a flux of 4.0 × 1012 photons s-1 at 1 Šinto a 1 µm × 1.5 µm to 10 µm × 10 µm (V × H) variable focus, expected to reach 5 × 1012 photons s-1 at final storage-ring current. This flux density surpasses most MX beamlines by nearly two orders of magnitude. The high brightness and microbeam capability of FMX are focused on solving difficult crystallographic challenges. The beamline's flexible design supports a wide range of structure determination methods - serial crystallography on micrometre-sized crystals, raster optimization of diffraction from inhomogeneous crystals, high-resolution data collection from large-unit-cell crystals, room-temperature data collection for crystals that are difficult to freeze and for studying conformational dynamics, and fully automated data collection for sample-screening and ligand-binding studies. FMX's high dose rate reduces data collection times for applications like serial crystallography to minutes rather than hours. With associated sample lifetimes as short as a few milliseconds, new rapid sample-delivery methods have been implemented, such as an ultra-high-speed high-precision piezo scanner goniometer [Gao et al. (2018). J. Synchrotron Rad. 25, 1362-1370], new microcrystal-optimized micromesh well sample holders [Guo et al. (2018). IUCrJ, 5, 238-246] and highly viscous media injectors [Weierstall et al. (2014). Nat. Commun. 5, 3309]. The new beamline pushes the frontier of synchrotron crystallography and enables users to determine structures from difficult-to-crystallize targets like membrane proteins, using previously intractable crystals of a few micrometres in size, and to obtain quality structures from irregular larger crystals.

Monolithic 3D printing of embeddable and highly stretchable strain sensors using conductive ionogels.

Medical training simulations that utilize 3D-printed, patient-specific tissue models improve practitioner and patient understanding of individualized procedures and capacitate pre-operative, patient-specific rehearsals. The impact of these novel constructs in medical training and pre-procedure rehearsals has been limited, however, by the lack of effectively embedded sensors that detect the location, direction, and amplitude of strains applied by the practitioner on the simulated structures. The monolithic fabrication of strain sensors embedded into lifelike tissue models with customizable orientation and placement could address this limitation. The demonstration of 3D printing of an ionogel as a stretchable, piezoresistive strain sensor embedded in an elastomer is presented as a proof-of-concept of this integrated fabrication for the first time. The significant hysteresis and drift inherent to solid-phase piezoresistive composites and the dimensional instability of low-hysteresis piezoresistive liquids inspired the adoption of a 3D-printable piezoresistive ionogel composed of reduced graphene oxide and an ionic liquid. The shear-thinning rheology of the ionogel obviates the need to fabricate additional structures that define or contain the geometry of the sensing channel. Sensors are printed on and subsequently encapsulated in polydimethylsiloxane (PDMS), a thermoset elastomer commonly used for analog tissue models, to demonstrate seamless fabrication. Strain sensors demonstrate geometry- and strain-dependent gauge factors of 0.54-2.41, a high dynamic strain range of 350% that surpasses the failure strain of most dermal and viscus tissue, low hysteresis (<3.5% degree of hysteresis up to 300% strain) and baseline drift, a single-value response, and excellent fatigue stability (5000 stretching cycles). In addition, we fabricate sensors with stencil-printed silver/PDMS electrodes in place of wires to highlight the potential of seamless integration with printed electrodes. The compositional tunability of ionic liquid/graphene-based composites and the shear-thinning rheology of this class of conductive gels endows an expansive combination of customized sensor geometry and performance that can be tailored to patient-specific, high-fidelity, monolithically fabricated tissue models.

Incorporation of the fluoroless C-Arm Trainer at the American Urological Association hands on training percutaneous renal access.

OBJECTIVES: To assess for usefulness and validity evidence for incorporating the C-Arm Trainer (CAT) simulator into the annual AUA hands on course for training percutaneous nephrolithotomy (PCNL). MATERIALS AND METHODS: The course started with a didactic session followed by four stations for training the "bull's eye" technique using the CAT simulator. Each station included a pre-test, 30-min practice on the simulator, and post-test. All participants were assessed using a 4-item checklist. All participants were asked to fill in a qualitative self-assessment questionnaire after the pre- and the post-test, and respond to a course evaluation questionnaire and post-course survey. RESULTS: A total of 38 physicians, who attended the hands on course, voluntarily participated in the study. Only 21.1% had previous practice on PCNL simulators. Compared with the results of the checklist total score and the qualitative self-assessment questionnaire scores after the pre-test, there was significant improvement in the checklist total score (p < 0.001), temporal demands (p = 0.003), situational stress (p = 0.003, and performance (0.003) after the post-test. A total of 14 (36%) participants responded to the course evaluation questionnaire, 50% evaluated the course as excellent, 28.6% as very good, and 21.4% as good. Unfortunately, only five (13%) participants responded to the post-course survey, 4/5 implemented the new competencies and knowledge into their practice, and 3/5 have attempted to obtain fluoroscopic guided PCA without assistance. CONCLUSION: The CAT simulator was considered useful for training the percutaneous renal access procedure. There was significant improvement in the qualitative and quantitative assessment parameters after the post-test compared with the pre-test.

Construct, content and face validity of the camera handling trainer (CHT): a new E-BLUS training task for 30° laparoscope navigation skills.

PURPOSE: Assessing construct, face and content validity of the camera handling trainer (CHT), a novel low-fidelity training device for 30° laparoscope navigation skills. METHODS: We developed a custom-designed box trainer with clinically based graphic targets. A total of 117 participants, stratified according to their previous experience (novice, competent, expert), took part to a CHT session and subsequently were asked to fill out a survey to assess the impact of the CHT on their 30° laparoscope navigation skills. Sixty of them were also studied for task performance during a 1-h session, with multiple time measurements. RESULTS: All participants, regardless of the previous experience, significantly improved their performance after the CHT session. Regarding construct validity, the mean task performance on the last measurement for novice group was found to be comparable to the mean first attempt of both competent (p = 0.12) and expert (p = 0.24) participants. All participants agreed that "the CHT is a valid training tool" and that "the CHT should be part of the regular dry laboratory training sessions", assessing both face and content validity. Limitations include the need for assessment of predictive validity. CONCLUSIONS: The CHT is a valid training tool for 30° laparoscope navigation and thus should be considered as one of the fundamental exercises during basic laparoscopic hands-on training sessions for urologists.

Preliminary evaluation of the SimPORTAL major vessel injury (MVI) repair model.

BACKGROUND: Major vessel injury (MVI) is a dangerous complication associated with laparoscopic surgery that leads, if not properly handled, to blood loss, conversion to open surgery, and eventually death. In this paper, we describe the preliminary evaluation of the SimPORTAL MVI model, created with the goal of simulating an intra-corporeal injury to a large vessel. METHODS: For this study, we created MVI models for 17 residents (PGY 1-4). Each resident was asked to perform an intracorporeal knot on a penrose drain within a maximum time limit of 6 min (in accordance with European basic laparoscopic urological skills rules) and then to subsequently repair a vessel injury on the MVI model, which was perfused with synthetic blood, within a maximum blood loss of 3 L. During the vessel repair, low lights and pulse sounds were used to simulate the operating room environment. All participants filled out a survey pre- and post-task to score various aspects of the model. RESULTS: We successfully created a model that simulates a critical surgical event. None of the participants reported having previous experience repairing a MVI. Six participants were able to perform the intracorporeal knot, and 12 residents (70.5%) were able to repair the MVI model under the given time and blood loss limits. Eleven participants agreed that the MVI model behaves like a real vessel, and six felt to be capable of performing the task prior to attempting it. Sixteen participants thought that the MVI model should be part of laparoscopic curriculums during residency. CONCLUSIONS: The SimPORTAL MVI model is a feasible low-cost model that would be well appreciated as a part of laparoscopic curriculum for residents. Minor improvements, including pressure measurement in the vessel for task assessment, will be made in the future, and further studies are necessary to definitively validate this model.

High throughput screening using acoustic droplet ejection to combine protein crystals and chemical libraries on crystallization plates at high density.

We describe a high throughput method for screening up to 1728 distinct chemicals with protein crystals on a single microplate. Acoustic droplet ejection (ADE) was used to co-position 2.5nL of protein, precipitant, and chemicals on a MiTeGen in situ-1 crystallization plate™ for screening by co-crystallization or soaking. ADE-transferred droplets follow a precise trajectory which allows all components to be transferred through small apertures in the microplate lid. The apertures were large enough for 2.5nL droplets to pass through them, but small enough so that they did not disrupt the internal environment created by the mother liquor. Using this system, thermolysin and trypsin crystals were efficiently screened for binding to a heavy-metal mini-library. Fluorescence and X-ray diffraction were used to confirm that each chemical in the heavy-metal library was correctly paired with the intended protein crystal. A fragment mini-library was screened to observe two known lysozyme ligands using both co-crystallization and soaking. A similar approach was used to identify multiple, novel thaumatin binding sites for ascorbic acid. This technology pushes towards a faster, automated, and more flexible strategy for high throughput screening of chemical libraries (such as fragment libraries) using as little as 2.5nL of each component.

Acoustic transfer of protein crystals from agarose pedestals to micromeshes for high-throughput screening.

Acoustic droplet ejection (ADE) is an emerging technology with broad applications in serial crystallography such as growing, improving and manipulating protein crystals. One application of this technology is to gently transfer crystals onto MiTeGen micromeshes with minimal solvent. Once mounted on a micromesh, each crystal can be combined with different chemicals such as crystal-improving additives or a fragment library. Acoustic crystal mounting is fast (2.33 transfers s(-1)) and all transfers occur in a sealed environment that is in vapor equilibrium with the mother liquor. Here, a system is presented to retain crystals near the ejection point and away from the inaccessible dead volume at the bottom of the well by placing the crystals on a concave agarose pedestal (CAP) with the same chemical composition as the crystal mother liquor. The bowl-shaped CAP is impenetrable to crystals. Consequently, gravity will gently move the crystals into the optimal location for acoustic ejection. It is demonstrated that an agarose pedestal of this type is compatible with most commercially available crystallization conditions and that protein crystals are readily transferred from the agarose pedestal onto micromeshes with no loss in diffraction quality. It is also shown that crystals can be grown directly on CAPs, which avoids the need to transfer the crystals from the hanging drop to a CAP. This technology has been used to combine thermolysin and lysozyme crystals with an assortment of anomalously scattering heavy atoms. The results point towards a fast nanolitre method for crystal mounting and high-throughput screening.

Multi-Institutional Validation of an OSATS for the Assessment of Cystoscopic and Ureteroscopic Skills.

PURPOSE: We evaluated the internal and construct validity of an assessment tool for cystoscopic and ureteroscopic cognitive and psychomotor skills at a multi-institutional level. MATERIALS AND METHODS: Subjects included a total of 30 urology residents at Ohio State University, Columbus, Ohio; Penn Presbyterian Medical Center, Philadelphia, Pennsylvania; and Mayo Clinic, Rochester, Minnesota. A single external blinded reviewer evaluated cognitive and psychomotor skills associated with cystoscopic and ureteroscopic surgery using high fidelity bench models. Exercises included navigation, basketing and relocation; holmium laser lithotripsy; and cystoscope assembly. Each resident received a total cognitive score, checklist score and global psychomotor skills score. Construct validity was assessed by calculating correlations between training year and performance scores (both cognitive and psychomotor). Internal validity was confirmed by calculating correlations between test components. RESULTS: The median total cognitive score was 91 (IQR 86.25, 97). For psychomotor performance residents had a median total checklist score of 7 (IQR 5, 8) and a median global psychomotor skills score of 21 (IQR 18, 24.5). Construct validity was supported by the positive and statistically significant correlations between training year and total cognitive score (r = 0.66, 95% CI 0.39-0.82, p = 0.01), checklist scores (r = 0.66, 95% CI 0.35-0.84, p = 0.32) and global psychomotor skills score (r = 0.76, 95% CI 0.55-0.88, p = 0.002). The internal validity of OSATS was supported since total cognitive and checklist scores correlated with the global psychomotor skills score. CONCLUSIONS: In this multi-institutional study we successfully demonstrated the construct and internal validity of an objective assessment of cystoscopic and ureteroscopic cognitive and technical skills, including laser lithotripsy.

Development and validation of a basic arthroscopy skills simulator.

PURPOSE: The purpose of our study was to develop a low-fidelity surgical simulator for basic arthroscopic skills training, with the goal of creating a pretrained novice ready with the basic skills necessary for all joint arthroscopic procedures. METHODS: A panel of education, arthroscopy, and simulation experts designed and evaluated a basic arthroscopic skills training and testing box. Task deconstruction was used to create 2 modules, which incorporate core skills common to all arthroscopic procedures. Core metrics measured were time to completion, number of trials to steady state, and number of errors. Face validity was evaluated using a questionnaire. Construct validity was examined by comparing 8 medical students with 8 expert orthopaedic surgeons. RESULTS: Surgeons were faster than students on both module 1 (P = .0013), simulating triangulation skills, and module 2 (P = .0190) simulating object manipulation skills. Surgeons demonstrated fewer errors (6.9 errors versus 28.1; P = .0073). All surgeons were able to demonstrate steady state (i.e., perform 2 trials that were within 10% of each other for time to completion and errors) on both modules within 3 trials on each module. Only 2 novices were able to demonstrate steady state on either module, and both did so within 3 trials. Furthermore, face validity of the skills trainer was shown by the expert arthroscopists. CONCLUSIONS: We describe a basic arthroscopy skills simulator that has face and construct validity. Our expert panel was able to design a simulator that differentiated between experienced arthroscopists and novices. CLINICAL RELEVANCE: Surgical simulation is an important part of efficient surgical education. This simulator shows good construct and face validity and provides a low-fidelity option for teaching the entry-level arthroscopist.

Hitting the target: fragment screening with acoustic in situ co-crystallization of proteins plus fragment libraries on pin-mounted data-collection micromeshes.

Acoustic droplet ejection (ADE) is a powerful technology that supports crystallographic applications such as growing, improving and manipulating protein crystals. A fragment-screening strategy is described that uses ADE to co-crystallize proteins with fragment libraries directly on MiTeGen MicroMeshes. Co-crystallization trials can be prepared rapidly and economically. The high speed of specimen preparation and the low consumption of fragment and protein allow the use of individual rather than pooled fragments. The Echo 550 liquid-handling instrument (Labcyte Inc., Sunnyvale, California, USA) generates droplets with accurate trajectories, which allows multiple co-crystallization experiments to be discretely positioned on a single data-collection micromesh. This accuracy also allows all components to be transferred through small apertures. Consequently, the crystallization tray is in equilibrium with the reservoir before, during and after the transfer of protein, precipitant and fragment to the micromesh on which crystallization will occur. This strict control of the specimen environment means that the crystallography experiments remain identical as the working volumes are decreased from the few microlitres level to the few nanolitres level. Using this system, lysozyme, thermolysin, trypsin and stachydrine demethylase crystals were co-crystallized with a small 33-compound mini-library to search for fragment hits. This technology pushes towards a much faster, more automated and more flexible strategy for structure-based drug discovery using as little as 2.5 nl of each major component.

Solvent minimization induces preferential orientation and crystal clustering in serial micro-crystallography on micro-meshes, in situ plates and on a movable crystal conveyor belt.

X-ray diffraction data were obtained at the National Synchrotron Light Source from insulin and lysozyme crystals that were densely deposited on three types of surfaces suitable for serial micro-crystallography: MiTeGen MicroMeshes™, Greiner Bio-One Ltd in situ micro-plates, and a moving kapton crystal conveyor belt that is used to deliver crystals directly into the X-ray beam. 6° wedges of data were taken from ∼100 crystals mounted on each material, and these individual data sets were merged to form nine complete data sets (six from insulin crystals and three from lysozyme crystals). Insulin crystals have a parallelepiped habit with an extended flat face that preferentially aligned with the mounting surfaces, impacting the data collection strategy and the design of the serial crystallography apparatus. Lysozyme crystals had a cuboidal habit and showed no preferential orientation. Preferential orientation occluded regions of reciprocal space when the X-ray beam was incident normal to the data-collection medium surface, requiring a second pass of data collection with the apparatus inclined away from the orthogonal. In addition, crystals measuring less than 20 µm were observed to clump together into clusters of crystals. Clustering required that the X-ray beam be adjusted to match the crystal size to prevent overlapping diffraction patterns. No additional problems were encountered with the serial crystallography strategy of combining small randomly oriented wedges of data from a large number of specimens. High-quality data able to support a realistic molecular replacement solution were readily obtained from both crystal types using all three serial crystallography strategies.

Macromolecular crystallography beamline X25 at the NSLS.

Beamline X25 at the NSLS is one of the five beamlines dedicated to macromolecular crystallography operated by the Brookhaven National Laboratory Macromolecular Crystallography Research Resource group. This mini-gap insertion-device beamline has seen constant upgrades for the last seven years in order to achieve mini-beam capability down to 20 µm × 20 µm. All major components beginning with the radiation source, and continuing along the beamline and its experimental hutch, have changed to produce a state-of-the-art facility for the scientific community.

Variability of tissue mechanical response in Sus Domesticus porcine models from in vivo to ex vivo conditions.

BACKGROUND: Healthcare simulators have been demonstrated to be a valuable resource for training several technical and nontechnical skills. A gap in the fidelity of tissues has been acknowledged as a barrier to application for current simulators; especially for interventional procedures. Inaccurate or unrealistic mechanical response of a simulated tissue to a given surgical tool motion may result in negative training transfer and/or prevents the "suspension of disbelief" necessary for a trainee to engage in the activity. Thus, where it is relevant to training outcomes, there should be an effort to create healthcare simulators with simulated tissue mechanical responses that match or represent those of biological tissues. Historically, this data is most often gathered from preserved (post mortem) tissue; however, there is a concern that the mechanical properties of preserved tissue, that lacks blood flow, may lack adequate accuracy to provide the necessary training efficacy of simulators. METHODS AND FINDINGS: This work explores the effect of the "state" of the tissue testing status on liver and peritoneal tissue by using a customized handheld grasper to measure the mechanical responses of representative porcine (Sus domesticus) tissues in n = 5 animals across five test conditions: in vivo, post mortem (in-situ), ex vivo (immediately removed from fresh porcine cadaver), post-refrigeration, and post-freeze-thaw cycle spanning up to 72 hours after death. No statistically significant difference was observed in the mechanical responses due to grasping between in vivo and post-freeze conditions for porcine liver and peritoneum tissue samples (p = 0.05 for derived stiffness at grasping force values F = 5N and 6.5N). Furthermore, variance between in vivo and post-freeze conditions within each animal, was comparable to the variance of the in vivo condition between animals. CONCLUSIONS: Results of this study further validate the use of preserved tissue in the design of medical simulators via observing tissue mechanical responses of post-freeze tissue comparable to in vivo tissue. Therefore, the use of thawed preserved tissue for the further study and emulation of mechanical perturbation of the liver and peritoneum can be considered. Further work in this area should investigate these trends further, particularly in regard to other tissues and the potential effects varying preservation methods may yield.