Breaking Earth's shell into a global plate network.

The initiation mechanism of Earth's plate tectonic cooling system remains uncertain. A growing consensus suggests that multi-plate tectonics was preceded by cooling through a single-plate lithosphere, but models for how this lithosphere was first broken into plates have not converged on a mechanism or a typical early plate scale. A commonality among prior efforts is the use of continuum mechanics approximations to evaluate this solid mechanics problem. Here we use 3D spherical shell models to demonstrate a self-organized fracture mechanism analogous to thermal expansion-driven lithospheric uplift, in which globe-spanning rifting occurs as a consequence of horizontal extension. Resultant fracture spacing is a function of lithospheric thickness and rheology, wherein geometrically-regular, polygonal-shaped tessellation is an energetically favored solution because it minimizes total crack length. Therefore, warming of the early lithosphere itself-as anticipated by previous studies-should lead to failure, propagating fractures, and the conditions necessary for the onset of multi-plate tectonics.

Post-traumatic orbital reconstruction: anatomical landmarks and the concept of the deep orbit.

Dissection deep within the orbit is a cause for concern to surgeons because of the perceived risks of injuring critical structures such as the contents of the superior orbital fissure and the optic nerve. Although "safe distances" (those distances within which it is considered safe to dissect within the orbit) have been described, these are of limited value if the orbit is severely disrupted or is congenitally shallow. In addition, traumatic defects in the orbital floor, in particular, often extend beyond these distances. Reliable landmarks based on the relations between anatomical structures within the orbit, rather than absolute distances, are described that permit safe dissection within the orbit. We present the concept of the deep orbit and describe its relevance to repair of injuries.

Resolution of diplopia after repair of the deep orbit.

The degree of resolution of diplopia after repair of a blow-out fracture of the orbital floor varies and depends on many factors. We present six patients, each of whom had extensive fractures of the floor of the orbit that extended posteriorly to its anatomical limit. The mean (range) time for the resolution of diplopia after reconstruction was 4.4 (1-7) months. We think that its slow resolution in these patients may require preoperative counselling, and also the postoperative management of patients with extensive disruptions of the floor of the orbit posterior to the anterior limit of the inferior orbital fissure (within the deep orbit) must be carefully planned.

Ethical decision making by nurses in HIV/AIDS situations.

The purpose of this study was to assess the ethical decision making levels of nurses in HIV/AIDS situations. Using an adapted form of Crisham's Nursing Dilemma Test, RNs in various settings in Ohio ranked their reasons for action in responding to vignettes. Findings suggest that nurses are basing their clinical decisions in HIV/AIDS situations on practical considerations rather than on nursing principles. Education programs based on the findings from this study will enhance the use of nursing principles.

Satisfaction with nursing care: a comparison of patients with HIV/AIDS, non-HIV/AIDS infectious diseases, and medical diagnoses.

The purpose of this study was to describe patients' perceptions of nursing care and compare those perceptions based on patients' diagnoses (HIV/AIDS, non-HIV/AIDS infectious diseases, and medical diagnoses). One hundred forty-two patients on five units in a major medical center were surveyed using the Patient Satisfaction Instrument. In addition, 126 staff nurses completed the AIDS Vulnerability Survey. Results of data analysis indicated a statistically significant difference in patient satisfaction with nursing care among patients in the medical group compared to patients in the HIV/AIDS group, with the medical group being more satisfied with their nursing care. Further, there was a statistically significant difference across units between nurses' knowledge, attitude, and fear. In spite of their knowledge base related to HIV/AIDS, nurses felt vulnerable when providing care to this population, thus perpetuating fear and negative attitudes. Additional research into the dynamics of these relationships is imperative as we continue to see increases in the number of patients with HIV/AIDS.

The blood-brain barrier and its role in inflammation.

The unique microenvironment within the central nervous system (CNS) relies upon the integrity of the blood-brain barrier (BBB). This selectively permeable barrier comprises interendothelial tight junctions located at the capillaries and postcapillary venules. Cells and structures in the local environment are required to maintain normal BBB function. When inflammation is present, the BBB itself plays an integral role in the inflammatory response by either producing or expressing a variety of cytokines, adhesion molecules, metalloproteinases, serine proteases, products of arachidonic acid metabolism, and nitric oxide. Understanding the role of the BBB during inflammation is essential when creating and employing a therapeutic regime for animals with CNS disease. This review focusses on recent discoveries about the BBB and its role in inflammation, and applies this knowledge to our current understanding of inflammatory CNS disease in dogs and cats.

Behavioural analysis of the efficacy of treatments for injuries to the spinal cord in animals.

There have been very few clinical trials evaluating therapies for naturally occurring spinal cord injury in dogs and cats. This review describes the methods suitable for evaluating the behavioural recovery of animals with spinal cord injuries, in either a clinical or a laboratory setting. A list of commonly used methods for evaluating behavioural recovery in animals is provided, both in the clinical and laboratory setting; the tests, their limitations and benefits and specific recommendations for their use are also discussed in more depth.

A descriptive study of missed appointments: families' perceptions of barriers to care.

INTRODUCTION: When clinic appointments are missed, families deprive their child of health care opportunities and contribute to rising health care costs. The purpose of this study was to determine families' perceptions of barriers to attending clinic appointments. METHOD: Two hundred participants with a history of missed appointments were randomly selected to participate in a telephone survey. Ninety-five of the families selected did not have telephones. Of the 105 families contacted by telephone, 101 consented to participate in a survey. For the group without phones (n = 95), demographic information was collected to use as comparison data with families that were reached. Patterns of missed appointments were also analyzed. RESULTS: The majority of families were headed by young single mothers. The families identified transportation problems, wait times, and not knowing the reason for the appointment as barriers. DISCUSSION: Clearly, many issues have an impact on decisions related to attending clinic appointments. In the interest of health, interventions to decrease barriers and increase attendance should be a priority for health care professionals. Further research of the effectiveness of these interventions will delineate the appropriate focus of health care professional's efforts.

Surgical management of cutaneous squamous cell carcinoma of the head and neck.

A retrospective audit was made of histological records and hospital case notes of patients who had cutaneous squamous cell carcinomas excised from the head and neck region at the Maxillofacial Units at St Richard's Hospital, Chichester and Southlands Hospital, Shoreham-By-Sea, UK. A total of 227 lesions were excised from 183 patients over a 5-year period between 1990 and 1995. The local recurrence rate was 4% (9/227) and 12 (7%) of the patients presented with or developed regional nodal metastases. Of the 183 patients, 177 (97%) were cured. These rates compare favourably with those of other published series of cutaneous squamous cell carcinoma managed by surgical techniques that did not follow the micrographical technique of Mohs. Certain characteristics may aid in the prediction of those cancers that may be more aggressive. It is important to evaluate each case in terms of histological grade and site and to design management plans to deal with each lesion in the most appropriate way.

Audit of a multidisciplinary approach to the care of children with unilateral and bilateral cleft lip and palate.

Cleft lip and palate affects the child in many ways, particularly appearance, dental arch relationships, growth of the face, and speech development. The key to successful care is management in a multidisciplinary team adhering to a well-designed protocol, and careful audit of results. We present the intermediate outcome audit of 15 patients with complete bilateral and unilateral cleft lip and palate whose condition was managed in a multidisciplinary team according to a strict protocol. We give the results observations of operations of a single surgeon's functional primary surgery over a 6-year period in terms of dental arch relationships, cephalometric analyses, aesthetic assessments, and speech analysis. The results show good early facial growth, with dental arch relationships appropriate for the age and group; we found only minor speech discrepancies, with no patients requiring pharyngoplasty. The results show the importance of multidisciplinary management, the value of keeping to sound surgical protocols, and functional techniques in cleft lip and palate surgery. Our study includes the neglected group of children who have bilateral cleft lip and palate, and it conforms to the style of pan-European projects.

Nursing students' knowledge and anxiety about AIDS: an experimental workshop.

The purpose of this quasiexperimental study was to examine the effectiveness of an experiential workshop on nursing students' anxiety and knowledge about AIDS. This study was based on Peplau's interpersonal theory in nursing practice. The sample included 67 senior nursing students and was designed as a three-group pre/post quasiexperiment. All groups received a pretest, posttest, and 6-week follow-up posttest. The experimental intervention was a 6-hour workshop that included anxiety awareness exercises in an experiential format and information about AIDS. Knowledge and anxiety scores were significantly higher for the group that attended the didactic portion of the workshop before the experiential portion. The control group showed no change in knowledge or anxiety. Results indicated that recognition of anxiety through experiential exercises contributed to learning about AIDS.

Intradural spinal arachnoid cyst in a dog.

An 8-month-old, spayed female dog was presented with signs localizing a neurologic lesion between the 3rd thoracic and 3rd lumbar vertebrae. An arachnoid cyst was diagnosed by myelography, and a dorsal laminectomy with durotomy was performed. The dog continues to do well 1-1/2 year after surgery.

Focal myasthenia gravis in a dog.

A 10-month-old American cocker spaniel was evaluated for megaesophagus, aspiration pneumonia, but no appendicular muscle weakness. During hospitalization, weakness of the facial muscles developed, this resolved with anticholinesterase administration. Serum antibodies against acetylcholine receptors were documented, confirming the diagnosis of focal myasthenia gravis. Diagnosis, management, and medical treatment are discussed.

Intravenous regional anesthesia (Bier block) in a dog.

Intravenous regional anesthesia was used in an adult dog as part of a balanced approach to general anesthesia for amputation of the 4th digit of its right hind limb. It allowed the concentration of isoflurane to be reduced to 0.5%.

An ethical model for decision-making.

The increasing social and technological complexity of health care is requiring health care providers to make many ethical decisions. This article presents a brief overview of selected ethical principles and theories, as well as several decision-making models. A 10-question model to assist the practitioner in assessing the moral aspects of an ethical dilemma is described and this model is applied to a clinical situation which involves the principles of confidentiality, autonomy, and prevention of harm.

Ethical decision making for community health nurses.

Modern health-care technology has complicated the ethical considerations of not only diagnosis and treatment, but also the social implications of diseases. Nurses are facing daily challenges as they struggle to protect and support confidentiality, justice, and beneficience for their clients. Community health nurses (CHNs), in light of their manner of primary care delivery, are often involved in these challenges. CHNs, due to their manner of primary care delivery, may find themselves in situations very different from those of other health-care workers. Often these situations have a moral component that cannot be addressed by the traditional problem-solving methods. Knowledge of ethical theories that offer frameworks for problem solving is essential as these CHNs struggle with ethical dilemmas.