Stability of supershort single-walled carbon nanotubes.

How short can single-walled carbon nanotubes (SWNTs) be? How stable are such supershort SWNTs (ss-SWNTs)? This work is the first to address these questions. On the basis of binding energy (E(B)), standard heats of formation , and strain energy (E(S)), we found that SWNTs with only one benzene ring in the axial direction, which we refer to as supershort SWNTs (ss-SWNTs), can be thermodynamically stable. On the basis of the data of E(B), , and E(S), the relative stabilities of ss-SWNTs, fullerenes, polycyclic aromatic hydrocarbons, and butadiyne are discussed. This study has laid a theoretical foundation for the possible synthesis of ss-SWNTs.

Gamete retrieval in terminal conditions.

There has been a growing interest and requests by patients facing intensive chemotherapy or surgically ablative procedures for gamete retrieval and preservation for future procreative efforts. There are technical difficulties in this area but little ethical discomfort. More troubling are the issues that arise with a terminally ill, incapable patient-one who is in a persistent vegetative state or who is declared brain dead or who is neurologically devastated with no hope for recovery, but not yet in either of the above states-or with a person who has suddenly died. In these cases, the surviving spouse, partner, or family members may request gamete retrieval for future reproductive efforts. Discussion of this topic within the Ethics Consultation Service at the University of Virginia demonstrated a need for development of insight derived from facts and ethical deliberation to help formulate a policy that would apply to such cases. A group was assembled with the expertise to explore the issue and to help formulate a policy that could be suggested for adoption by the hospital administration. The group consisted of a urologist with experience in sperm retrieval from terminally ill patients; the director of the laboratory supporting the assisted reproductive facility in the Department of Obstetrics and Gynecology; the chairperson of the Ethics Consultation Service (who is also a neonatologist); and 2 members of the Ethics Consultation Service, one a genetic counselor and the other an obstetrician-gynecologist with a master's degree in biomedical ethics. Current literature was reviewed, the expertise of the urological member and the reproductive laboratory director was explored, and the insight of the members of the Ethics Consultation Service was added. We explored the technical aspects of both male and female gamete retrieval and preservation and the reproductive potential of these stored gametes. We present a review of the current literature on both the technical and ethical aspects of the topic. Finally, we present a policy that we deem acceptable for adoption and that should be of value to other practitioners and facilities as they contemplate facing requests for gamete retrieval.

Ethical theory and principles: do they have any relevance to problems arising in everyday practice?

This review of ethical theories with application to two difficult obstetric cases will allow the practicing obstetrician and gynecologist to use these theories to help resolve difficult ethical dilemmas. In the first case a pregnant human immunodeficiency virus-infected woman refuses to take triple preventive therapy, with potential fetal harm. In the second case a couple with a quintuplet multifetal pregnancy needs assistance to decide about selective termination to effect fetal reduction.

Cerebral arteriovenous malformation in pregnancy: presentation and neurologic, obstetric, and ethical significance.

Cerebral arteriovenous malformations infrequently complicate pregnancy. We sought to determine the neurologic, obstetric, and ethical significance of such malformations. We present the clinical course of 2 pregnant women with arteriovenous malformations who experienced cerebral hemorrhage and a loss of capacity for decision making. We also review the neurologic and obstetric significance of arteriovenous malformations in pregnancy. Various treatment options with concern for pregnancy and the prognosis for arteriovenous malformations are outlined. The ethical issues involved for pregnant patients whose decisional capacity is compromised as a result of cerebral injury are explored. A review of persistent vegetative state and brain death (death by neurologic criteria) occurring in pregnancy allows us to explore many issues that are applicable to decisionally incapacitated but physiologically functioning pregnant women. We outline a document, the purpose of which is to obtain advance directives from pregnant women regarding end-of-life decisions and to appoint a surrogate decision maker. We believe that evaluation and treatment of the arteriovenous malformation may be undertaken without regard for the pregnancy and that the pregnancy should progress without concern for the arteriovenous malformation.

The fetal-pelvic index has minimal utility in predicting fetal-pelvic disproportion.

OBJECTIVE: Our purpose was to evaluate the fetal-pelvic index in our patient population and to determine whether it would be predictive of route of delivery. STUDY DESIGN: One hundred seventy-six patients with a previous history or clinical findings in the current pregnancy suggestive of fetal-pelvic disproportion participated in this Human Investigation Committee-approved study. All underwent fetal ultrasonographic examinations and modified digital radiography before labor. Fetal head and abdominal circumferences and maternal inlet and midpelvic circumferences were determined, and the fetal-pelvic index was calculated. RESULTS: Ninety-one patients fulfilled all aspects of the study, including rigorous criteria pertaining to labor management. Thirty of these patients underwent cesarean delivery and 61 were delivered vaginally. The fetal-pelvic index value for the vaginal delivery group was -5.4 +/- 5.3, as opposed to -2.4 +/- 5.8 in the cesarean delivery group (P <.02). Notwithstanding this difference, the fetal-pelvic index had a low overall ability to predict fetal-pelvic disproportion (0.65) and had associated sensitivity and specificity of 0.27 and 0.84, respectively. Predictive thresholds other than zero were tested, but optimal predictive ability, at a fetal-pelvic index cutoff of 2, was only 70% (sensitivity 0.20, specificity 0.95). CONCLUSION: In our patient population the fetal-pelvic index was only moderately predictive of fetal-pelvic disproportion. Factors other than those assessed by the fetal-pelvic index are probably important in determining the route of delivery. Further studies are indicated.

Ethical issues in managed care for the obstetrician and gynecologist.

The practice of medicine is now managed. Of this there is no doubt. The individual physician is placed in an ever-increasingly vulnerable position. He or she must cope with a myriad of contractual arrangements with strange concepts such as "withholds," "capitation," "covered lives," "limited liability on the part of the managed care organization;" "outcomes analysis," "practice guidelines," and, last but not least, "gag rules." Patients are being denied care that the physician may consider, if not essential, at least most desirable. On the one hand, the physician must serve a fiduciary obligation to the patient and act as the patient's advocate; on the other hand, the physician's income may be proportionally dependent on limiting the extent of the patient's access to unlimited care. The physician may be limited by restrictions imposed by the managed care organization as to what disclosures he or she may make to the patient regarding limitations of care. We will explore these issues from an ethical perspective and attempt to offer some insights on the basis of a review of the comments of many knowledgeable commentators on this topic, and we will explore the virtues that physicians will need to rely on to come to grips with the dilemmas they will face in the future with managed care.

Parental rights at the birth of a near-viable infant: conflicting perspectives.

OBJECTIVE: Our purpose was to clarify the roles of parents and caregivers in making decisions for resuscitation of near-viable infants. STUDY DESIGN: We present two cases and review ethical and legal issues involved in making decisions for near-viable infants. RESULTS: Medical responsibility for the infant shifts at birth from obstetrics to neonatology. Neonatologists will "opt for life" when prognosis is uncertain. As surrogate decision makers, parents have rights to make decisions about initiation of resuscitation, but these parental rights are limited by the infant's best interests. If caregivers believe parents are not acting in the infant's best interests, they may persuade parents, challenge parental refusal by petitioning the courts, or treat without consent with possible legal risk. CONCLUSIONS: Effective communication is essential to prevent misunderstanding and conflicts. In most instances parents are the best decision makers for a near-viable infant. Parental rights are limited by best interests of the infant.

Fetal radiation exposure is minimal after pelvimetry by modified digital radiography.

OBJECTIVE: Our purpose was to determine the maximal fetal exposure to radiation by use of thermoluminescent dosimeters when pelvic measurements were performed by standard or modified digital radiography. STUDY DESIGN: Digital radiography of the pelvis was performed according to a standard technique. Lithium fluoride thermoluminescent dosimeters were positioned on the patient's skin to quantitate the maximal amount of radiation exposure to the fetus. The standard technique often included a portion of fetal vertex. The axial view technique was modified to use an angle of inclination of 17 to 29 degrees relative to the vertical axis. RESULTS: Digital radiography was well tolerated and interpretable images were consistently obtained. The maximal dose to the fetal vertex by use of the standard digital axial slice was 465 mrad. By modifying the standard digital technique and using an angle of inclination of 17 to 29 degrees it was possible to obtain an axial section without including any portion of the fetal vertex. This reduced the maximal total dose to the fetal vertex to 55 mrad, which is less than the background radiation exposure to the fetus over a 9-month period from natural sources. CONCLUSION: Data reported indicate that total fetal radiation exposure is minimal after pelvimetry by digital radiography. Incorporating the modification of the angle for the axial slice, as reported here, resulted in a further significant decrease in fetal radiation exposure.

Resolving the clinical and ethical dilemma involved in fetal-maternal conflicts.

A serious ethical dilemma occurs when a pregnant woman refuses a medically indicated intervention. Should respect for her autonomy preclude any approach other than to accept her decision? Should the caregivers have recourse to "gentle persuasion"? Is there ever a justification for invoking the power of court-ordered intervention? The societal views on this subject are first developed from an ethical perspective. The pertinent court cases that reflect on this topic are reviewed. The process of developing guidelines within our institution is related. Finally, the guidelines that were eventually developed are offered.

Ethical considerations of managed care.

Universal health care will soon be here. This paper presents the basic models of managed care as well as a glossary of terms to allow discussion of the basic plans. Three cases are discussed to illustrate the dilemmas of managed care utilizing Dr. Fletcher's ethical model. Basic concepts are derived from these cases to assist physicians to work within the constraints of the new health care systems and enable them to respond to the sometimes unavoidable conflicts between medical benefit and cost containment.