Target structure induced suppression of the ionization cross section for very low energy antiproton-hydrogen collisions.

Low energy antiprotons have been used previously to give benchmark data for theories of atomic collisions. Here we present measurements of the cross section for single, nondissociative ionization of molecular hydrogen for impact of antiprotons with kinetic energies in the range 2-11 keV, i.e., in the velocity interval of 0.3-0.65 a.u. We find a cross section which is proportional to the projectile velocity, which is quite unlike the behavior of corresponding atomic cross sections, and which has never previously been observed experimentally.

Ionization of helium and argon by very slow antiproton impact.

The total cross sections for single ionization of helium and single and double ionization of argon by antiproton impact have been measured in the kinetic energy range from 3 to 25 keV using a new technique for the creation of intense slow antiproton beams. The new data provide benchmark results for the development of advanced descriptions of atomic collisions and we show that they can be used to judge, for the first time, the validity of the many recent theories.

The human micro-vascular endothelial cells in vitro interaction with atomic-nitrogen-doped diamond-like carbon thin films.

This paper reports the initial response of atomic nitrogen doped diamond like carbon (DLC) to endothelial cells in vitro. The introduction of nitrogen atoms/molecules to the diamond like carbon structures leads to an atomic structural change favorable to the attachment of human micro-vascular endothelial cells. Whilst the semi-conductivity induced by nitrogen in DLC is thought to play a part, the increase in the non-bonded N atoms and N(2) molecules in the atomic doped species (with the exclusion of the charged species) seems to contribute to the improved attachment of human microvascular endothelial cells. The increased endothelial attachment is associated with a lower work function and slightly higher water contact angle in the atomic doped films, where the heavy charged particles are excluded. The films used in the study were synthesized by the RF PECVD technique followed by post deposition doping with nitrogen, and afterwards the films were characterized by XPS, Raman spectroscopy, SIMS and Kelvin probe. The water contact angles were measured, and the counts of the adherent endothelial cells on the samples were carried out. This study is relevant and contributory to improving biocompatibility of surgical implants and prostheses.

Damage to plasmid DNA induced by low energy carbon ions.

The damage induced in supercoiled plasmid DNA molecules by 1-6 keV carbon ions has been investigated as a function of ion exposure, energy and charge state. The production of short linear fragments through multiple double strand breaks has been demonstrated and exponential exposure responses for each of the topoisomers have been found. The cross section for the loss of supercoiling was calculated to be (2.2 +/- 0.5) x 10(-14) cm(2) for 2 keV C(+) ions. For singly charged carbon ions, increased damage was observed with increasing ion energy. In the case of 2 keV doubly charged ions, the damage was greater than for singly charged ions of the same energy. These observations demonstrate that ion induced damage is a function of both the kinetic and potential energies of the ion.

Human microvascular endothelial cellular interaction with atomic N-doped DLC compared with Si-doped DLC thin films.

This article reports results of endothelial cell interaction with atom beam source N-doped a-C:H (diamond-like carbon, DLC) as it compares with that of Si-doped DLC thin films. The RF plasma source exhibits up to 40% N-dissociation and N-atomic fluxes of approximately 0.85 x 10(18) atoms/s, which ensures better atomic nitrogen incorporation. Two different types of nitrogen species (with and without the use of sweep plates to remove charged ions) were employed for nitrogen doping. The number of attached endothelial cells is highest on Si-DLC, followed by the N-DLC (where the sweep plates were used to remove ions), the N-DLC (without the use of sweep plates), undoped DLC, and finally the uncoated sample. The contact angle values for these films suggest that water contact angle is higher in the atomic nitrogen neutral films and Si-DLC films compared to the ionized-nitrogen specie doped films and undoped DLC thin films, suggesting that the more hydrophobic films, semiconducting films, and film with relieved stress have better interaction with human microvascular endothelial cells. It seems evident that N-doping increases the Raman I(D)/I(G) ratios, whereas N-neutral doping decreases it slightly and Si-doping decreases it even further. In this study, lower Raman I(D)/I(G) ratios are associated with increased sp(3)/sp(2) ratio, an increased H concentration, photoluminescence intensity, and a higher endothelial cellular adhesion. These investigations could be relevant to biocompatibility assessment of nanostructured biomaterials and tissue engineering.

Dynamic bone imaging in the differential diagnosis of skeletal lesions.

Dynamic bone imaging differs from routine multiphase bone scintigraphy by the use of time-activity curves (TACs) and quantitation of data. TACs were divided into an arterial plus blood pool phase (first 60 s at 1 frame/s) and a subsequent early bone uptake phase (24 min at 1 frame/min). Ratios of normalized integrals, from analogous regions were calculated to determine whether blood flow was abnormal. A key feature of the technique is the monitoring of the flow proximally and distally to the area of involvement. This was of importance in distinguishing between two diseases producing the same degree of local hyperemia. Dynamic bone imaging was applied to the differential diagnosis of arthritis, septic arthritis, cellulitis, osteomyelitis, tumor, avascular necrosis, Charcot joint, Legg-Perthes (LP) disease, and Osteochondritis Dissecans (OCD). Although the method is straightforward, there are technical and clinical factors that may affect interpretation of data. Asymmetries in flow may arise due to injection technique, interfering activity of bladder and/or bowel, vascular abnormalities, AV malformation, and venous backflow. The dynamic study is also sensitive to the effects of various modes of therapy. Consideration must be given to these technical and clinical factors for the avoidance of pitfalls in interpretation of the dynamic study.

Differentiation of Charcot joint from osteomyelitis through dynamic bone imaging.

The bone scans of 25 patients with a clinical diagnosis of diabetic osteoarthropathy (Charcot joint) of the ankle and foot were analysed using the technique of dynamic bone imaging. The analysis of time-activity curves generated over the Charcot joint, the contralateral joint and the bone above the Charcot joint, produces characteristic patterns that are distinguishable from the ones observed for osteomyelitis. Recently it has been shown that the significance of dynamic bone imaging resides in its correlation to physiological and morphological components of bone. The difference in the blood supply to the long bones has been suggested as an explanation for the difference in time-activity curve patterns.

Pathophysiologic interpretation of time activity curves in dynamic bone imaging.

Reported here is a theoretical model based on a literature review correlating the 60 sec/25 min time activity curves (TAC) of dynamic bone imaging with the histologic components of bone. Information regarding healing versus nonhealing as well as a histophysiologic description of ongoing disease is obtainable from TACs of paired disease and nondiseased limbs. The TACs reflect the movement of Tc-99m MDP complexes across histologic compartments to reach the amorphous calcium phosphate (ACP) regions. These complexes must exit the bone capillaries, pass through the perivascular space, cross the osteoblastic barrier, enter the bone fluid space, and traverse collagen osteoid to reach ACP. The presence of diseases such as osteomyelitis, cellulitis, and degenerative arthritis and septic arthritis variously affect these spaces to cause typical perturbations in the TACs. The distinction of these patterns were observed in 48 patients, 12 per category. The model that explains how 60 sec/25 min TACs can reflect the histologic status of ongoing bone disease was applied to these disorders.

Computerized blood flow analysis for decision making in the treatment of osteochondritis dissecans.

Patients presenting the radiologic appearance of osteochondritis dissecans (OCD) require a decision as to further treatment. This often requires an invasive procedure. The noninvasive technique of computerized blood flow analysis (CBFA) has been used in 13 patients with OCD. In clinically early disease (four patients), there is always decreased flow in the area distal to the OCD lesion. Patients with intermediate OCD (four patients) showed characteristics of healing reflected in increased flow to the OCD lesion. These patients were left under observation and underwent spontaneous healing. Patients who showed no increase in flow or had decreased flow in the area of involvement (four patients) were clinically found to be nonviable OCD and required surgical intervention. The technique of CBFA therefore holds promise for decision making in the management of this disease.

Dynamic bone scintigraphy in osteochondritis dissecans.

We report a retrospective study of eighteen patients with pain in the knee or ankle, eleven of whom had osteochondritis dissecans. In these patients the bone-flow time-activity curves were observed after an intravenous injection of a bolus of 99mTc MDP. The curves varied according to the severity of the clinical signs and symptoms. The diagnosis rate was 29% with static scintigraphy and this improved to 57% when dynamic flow studies were used. A positive pattern in the dynamic study together with radiographs and static scintigraphs raised the diagnosis rate to 100%; the sensitivity was 90%. These preliminary results show that dynamic bone scintigraphy holds promise as a technique for identification and management of this condition.

Computerized blood-flow analysis in osteochondritis dissecans.

A retrospective review of static images and computerized blood flow studies (CBFS) in patients with osteochondritis dissecans (OCD) suggests that CBFS maybe useful in following the clinical course of this disease.

Congenital spleen thinning mimicking a space-occupying lesion.

By splenic imaging, a large focal defect was demonstrated in a symptomatic South American immigrant with simultaneous parasitic infestation of strongyloidiasis and entamebiasis. The CT scan also was thought to be abnormal. Pathologic findings reported a variation in splenic configuration. Unusual splenic configuration should be considered in the differential diagnosis of abnormal scans.

The fixation disparity-heterophoria relationship.

If the heterophoria is the cause of a fixation disparity, then certain conditions can be experimentally observed. An experiment was performed and the conditions previously set forth as indicative of a cause-effect relationship between the heterophoria and fixation disparity were observed.