Electrodeposited polytyramine as an immobilisation matrix for enzyme biosensors

The application of an electrodeposited polytyramine film as an immobilisation matrix for the construction of enzyme biosensors is described. Glucose oxidase (used as a model enzyme) is covalently attached to free amine groups on the polytyramine film using the coupling reagents 1-ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide. The resultant recognition interface consisted of multilayers of GOx immobilised onto the polymer surface. This method of constructing enzyme biosensors is shown to produce a highly reproducible and stable device. The biosensor showed no loss in electrode response after four months of dry storage and exhibited only minor loss in response after 20 days of repeated use. The resultant biosensor had a linear range of 0.1-28 mM glucose and a detection limit of 0.01 mM.     

An experimental evaluation of traumatic globe rupture

PURPOSE: The purpose of this investigation was to evaluate the surgeon's ability to assess various types of globe injury, to determine the force necessary to rupture the globe with these types of injuries, and to determine typical orbital retraction forces used in the clinical setting. MATERIALS AND METHODS: Forty-four enucleated globes from recently killed cows were divided into four equal groups-one uninjured control group, one group with a through-and-through scleral laceration, another group with a subtotal scleral laceration, and the last group with an 18-gauge needle perforation. Twenty-seven boarded or board eligible oral and maxillofacial surgeons were asked to assess one sample from each of the four groups. They were then asked to retract a simulated globe on a custom-fabricated jig to determine clinical retraction forces. Ten globes from each of the four groups were then subjected to forces until rupture on an Instron 8501M mechanical testing unit. Accuracy of the clinical assessment was determined, and means and standard deviations of the retraction forces and globe rupture forces were derived. RESULTS: Through-and-through lacerations were assessed by surgeons with 100% accuracy, subtotal lacerations with 96% accuracy, uninjured globes with 74% accuracy, and perforated globes with 15% accuracy. Globe rupture occurred at 16.72+/-7.87 kg in the control group, 20.36+/-7.87 kg in the perforated group, 15.38+/-6.06 kg in the subtotal laceration group, and 4.94+/-2.56 kg in the through-and-through laceration group. Statistically significant differences (P < .001) were noted between the total laceration group and all other groups. The mean retraction force was 0.35+/-0.47 kg, which was statistically less than the force used in all of the rupture groups (P < .001). CONCLUSIONS: Severe injuries (through-and-through lacerations) were assessed with 100% accuracy by the clinicians, and less severe injuries with less accuracy. Rupture forces for globes with perforations and subtotal lacerations were no different than for the control group, but substantially less than for the total laceration group. The simulated clinical retraction forces were substantially more than the rupture forces in all of the groups, including the through-and-through laceration group.     

Geographic variations in the composition of ivory of the African elephant (Loxodonta africana)

OBJECTIVES: The purpose of the present study was to compare the inclination of the occlusal plane with occlusal guidance as a contributing factor to masticatory movement. METHODS: Masticatory movements of 41 young adults were measured using a 3-D mandibular movement analysing system. The inclination of the occlusal plane was measured in the sagittal plane using a 3-D digitizer. The contribution of the occlusal guidance and the inclination of the occlusal plane to the direction of the masticatory path of closure was evaluated at various closing levels. RESULTS: The masticatory path of closure outside the intercuspal range was influenced mainly by the inclination of the occlusal plane, and the masticatory path of closure near the intercuspal range was only influenced by occlusal guidance. The so-called gliding type masticatory pattern was observed predominantly in subjects with a posteriorly inclined occlusal plane. In contrast, a chopping type masticatory pattern was observed predominantly in subjects with an anteriorly inclined occlusal plane. CONCLUSIONS: The contribution of the inclination of the occlusal plane to masticatory movement was greater than that of occlusal guidance throughout the closing phase except near the intercuspal range.     

A novel k-space trajectory measurement technique

OBJECTIVE: To report our experience with erosion of permanent suture or mesh material after abdominal sacrocolpopexy. METHODS: A retrospective chart review was performed to identify patients who underwent sacrocolpopexy by the same surgeon over 8 years. Demographic data, operative notes, hospital records, and office charts were reviewed after sacrocolpopexy. Patients with erosion of either suture or mesh were treated initially with conservative therapy followed by surgical intervention as required. RESULTS: Fifty-seven patients underwent sacrocolpopexy using synthetic mesh during the study period. The mean (range) postoperative follow-up was 19.9 (1.3-50) months. Seven patients (12%) had erosions after abdominal sacrocolpopexy with two suture erosions and five mesh erosions. Patients with suture erosion were asymptomatic compared with patients with mesh erosion, who presented with vaginal bleeding or discharge. The mean (+/-standard deviation) time to erosion was 14.0+/-7.7 (range 4-24) months. Both patients with suture erosion were treated conservatively with estrogen cream. All five patients with mesh erosion required transvaginal removal of the mesh. CONCLUSION: Mesh erosion can follow abdominal sacrocolpopexy over a long time, and usually presents as vaginal bleeding or discharge. Although patients with suture erosion can be managed successfully with conservative treatment, patients with mesh erosion require surgical intervention. Transvaginal removal of the mesh with vaginal advancement appears to be an effective treatment in patients failing conservative management.     

Effects of accelerated testing on porcine bioprosthetic heart valve fiber architecture

We undertook the following study to quantitatively assess the changes in porcine bioprosthetic heart valve (PBHV) fiber architecture to increasing levels of fatigue damage using an in vitro accelerated test model. PBHVs were subjected to 0-500 million test cycles at 16 Hz, and small-angle light scattering (SALS) was used to quantify the gross fiber structure of the cusps. The degree of gross fiber alignment remained essentially constant from 0 to 500 million cycles over the entire cusp. Increasing fiber orientation randomness, indicative of local damage, was observed only in the vicinity of the nodulus of Arantii after 50 million cycles. The SALS data from the damaged regions suggested shearing between fiber layers, which may be part of the failure process and accelerates valve failure. Histological analysis revealed a relatively intact gross fiber structure with the collagen fiber crimp remaining, although delamination and de-registration of the crimp was also observed. Accelerated tested PBHVs also demonstrated a pronounced 'sagging', which began at the earliest cycle number tested (1.4 million cycles) and whose rate decreased logarithmically with cycle number. Results of this study suggest that PBHV cusps can alter their shape without any visually apparent material yielding or fiber failure under continual cyclic loading. Further, while most of the 4 mmHg pressure fixed PBHV's gross fiber architecture remains unchanged after 500 million cycles of accelerated testing, localized accumulated fiber damage can occur on a sub-visual structural level as early as 50 million cycles.     

The nitric oxide-cGMP pathway may mediate communication between sensory afferents and projection neurons in the antennal lobe of Manduca sexta

The nitric oxide (NO)-cGMP signaling system is thought to play important roles in the function of the olfactory system in both vertebrates and invertebrates. One way of studying the role of NO in the nervous system is to study the distribution and properties of NO synthase (NOS), as well as the soluble guanylyl cyclases (sGCs), which are the best characterized targets of NO. We study NOS and sGC in the relatively simple and well characterized insect olfactory system of the hawkmoth, Manduca sexta. We have cloned Manduca sexta nitric oxide synthase (MsNOS) and two sGCs (MsGCalpha1 and MsGCbeta1), characterized their basic biochemical properties, and studied their expression in the olfactory system. The sequences of the Manduca genes are highly similar to their mammalian homologs and show similar biochemical properties when expressed in COS-7 cells. In particular, we find that MsGC functions as an obligate heterodimer that is stimulated significantly by NO. We also find that MsNOS has a Ca2+-sensitive NO-producing activity similar to that of mammalian neuronal NOS. Northern and in situ hybridization analyses show that MsNOS and the MsGCs are expressed in a complementary pattern, with MsNOS expressed at high levels in the antennae and the MsGCs expressed at high levels in a subset of antennal lobe neurons. The expression patterns of these genes suggest that the NO-sGC signaling system may play a role in mediating communication between olfactory receptor neurons and projection neurons in the glomeruli of the antennal lobe.     

Retail yield and fabrication times for veal as influenced by purchasing options and merchandising styles

Twenty-nine selected styles of subprimals or sections of veal were obtained from a commercial facility to assist in the development of a support program for retailers. They were fabricated into bone-in or boneless retail cuts and associated components by trained meat cutters. Each style selected (n = 6) was used to generate mean retail yields and labor requirements, which were calculated from wholesale and retail weights and processing times. Means and standard errors for veal ribs consisting of five different styles (n = 30) concluded that style #2, 7-rib 4 (10 cm) x 4 (10 cm), had the lowest percentage of total retail yield (P < .05) owing to the greatest percentage of bone. Furthermore, rib style #2 required the longest total processing time (P < .05). Rib styles #3, 7-rib chop-ready, and #5, 6-rib chop ready, yielded the greatest percentage of total retail yield and also had the shortest total processing time (P < .05). Within veal loins, style #2, 4 (10 cm) x 4 (10 cm) loin kidney fat in, had the greatest percentage fat (P < .05). Loin styles #2 and #3, 4 (10 cm) x 4 (10 cm) loin special trimmed, generated more lean and fat trimmings and bone, resulting in lower percentage of total retail yields than loin style #1, 0 (0 cm) x 1 (2.5 cm) loin special trimmed (P < .05). Results indicated that bone-in subprimals and sections required more processing time if fabricated into a boneless end point. In addition, as the number of different retail cuts increased, processing times also increased.     

Differential expression and distribution of focal adhesion and cell adhesion molecules in rat hepatocyte differentiation

The present study has examined the distribution of axons of differing sizes in the optic pathway of the ground squirrel. Axon diameters were measured from electron micrographs at various locations across sections of the optic nerve and tract, and total distributions and numbers were estimated. In both the nerve and tract, roughly 1.2 million optic axons were present. The population of optic axons had a unimodal size distribution, peaking at 0.9 microm in diameter and having an extended tail toward larger diameters. Local axon diameter distributions in the optic tract indicated distinct (though partially overlapping) axon diameter classes, including one of fine sizes peaking at 0.8-0.9 microm, a second of medium sizes peaking around 1.7-1.8 microm, and a third composed of the larger fibers with diameters up to 4.8 microm. The fine-caliber axons were found at all locations in the tract, and were the only axons present immediately adjacent to the pia, while the medium- and coarse-caliber axons were found at deeper locations. Curiously, the larger axons were found primarily in the medial parts of the tract, where axons from the dorsal retina normally course. A similarly restricted distribution of the larger axons was observed in the dorsotemporal parts of the optic nerve, suggesting that this difference in the tract may relate to an asymmetric distribution of ganglion cells on the retina giving rise to these axons. Measurements of axonal size taken within the optic fiber layer in dorsal and ventral parts of the retina confirmed this asymmetry, consistent with previous demonstrations of soma size differences in the dorsal versus ventral retina. The partial segregation of axons by size in the optic tract of the ground squirrel then reflects both the asymmetric distribution of retinal ganglion cell classes and the chronotopic reordering of optic axons that occurs within the chiasmatic region.     

Translational motion compensation for coronary angiogram sequences

A method of compensating for the lag of the video cameras typically used in angiographic systems is presented for use in sequences of digitized X-ray images. The lag effect is reduced by a straightforward weighted subtraction, which has the undesirable side effect of increasing noise. By superimposing several lag-corrected and appropriately shifted images, however, the signal-to-noise ratio can be restored. The algorithm uses the phase-correlation method to measure the two-dimensional shift of a mobile coronary arterial structure. Processing is confined to a rectangular area of interest (AOI), which encloses a feature of clinical significance. The differences of the phases of the Fourier transforms of two frames is computed, combined with an appropriate filter, and inverse Fourier-transformed to produce a phase-correlation image. The vector separation from the origin of image space of the peak of the phase-correlation image is the estimate of the shift of the artery's position in the second frame as compared to the first. The isolation of the AOI from the surrounding image is achieved by the application of a window and correction for any linear trend in the background intensity.     

On detecting co-resident cloud instances using network flow watermarking techniques

Virtualization is the cornerstone of the developing third-party compute industry, allowing cloud providers to instantiate multiple virtual machines (VMs) on a single set of physical resources. Customers utilize cloud resources alongside unknown and untrusted parties, creating the co-resident threat—unless perfect isolation is provided by the virtual hypervisor, there exists the possibility for unauthorized access to sensitive customer information through the exploitation of covert side channels. This paper presents co-resident watermarking, a traffic analysis attack that allows a malicious co-resident VM to inject a watermark signature into the network flow of a target instance. This watermark can be used to exfiltrate and broadcast co-residency data from the physical machine, compromising isolation without reliance on internal side channels. As a result, our approach is difficult to defend against without costly underutilization of the physical machine. We evaluate co-resident watermarkingunder a large variety of conditions, system loads and hardware configurations, from a local laboratory environment to production cloud environments (Futuregrid and the University of Oregon’s ACISS). We demonstrate the ability to initiate a covert channel of 4 bits per second, and we can confirm co-residency with a target VM instance in $<$ 10 s. We also show that passive load measurement of the target and subsequent behavior profiling is possible with this attack. We go on to consider the detectability of co-resident watermarking, extending our scheme to create a subtler watermarking attack by imitating legitimate cloud customer behavior. Our investigation demonstrates the need for the careful design of hardware to be used in the cloud.