Variation in the circularly polarized light reflection of Lomaptera (Scarabaeidae) beetles.

An extended spectroscopic study on the left-through-left circularly polarized reflection spectra of a large number of beetles from the Australasian Scrabaeidae:Cetoniinae of the Lomaptera genus was undertaken. We have obtained a five-category spectral classification. The principal spectral features, which even within the genus range from blue to infrared, are related to structural chirality in the beetle shells. The detailed features of each spectral classification are related to different structural perturbations of the helix, including various pitch values and abrupt twist defects. These spectral characteristics and associated shell structures are confirmed on the basis of simple modelling. An important conclusion from our study is that the simple helical structure resulting in a single symmetric Bragg peak is not the dominant spectral type. Rather the reality is a rich tapestry of spectral types. One intriguing specimen is identified via a scanning electron micrograph to consist of a double interstitial helix leading to a particular double-peak spectrum.

Causality-based criteria for a negative refractive index must be used with care.

Using the principle of causality as expressed in the Kramers-Kronig relations, we derive a generalized criterion for a negative refractive index that admits imperfect transparency at an observation frequency omega. It also allows us to relate the global properties of the loss (i.e., its frequency response) to its local behavior at omega. However, causality-based criteria rely on the group velocity, not the Poynting vector. Since the two are not equivalent, we provide some simple examples to compare the two criteria.

Mohs micrographic surgery for lentigo maligna and lentigo maligna melanoma. A follow-up study.

BACKGROUND: We previously reported our experience using Mohs micrographic surgery (MMS) for 45 patients with lentigo maligna (LM) and lentigo maligna melanoma (LMM). The patients were treated between 1985 and 1992. In our initial publication, all of the patients were free of local disease and evidence of metastases at an average of 29.2 months after therapy. OBJECTIVE: The purpose of this study was to report long-term follow-up of our previously published data. METHODS: MMS was performed in 26 patients with LM and 19 patients with LMM using frozen sections followed by rush permanent sections. Follow-up was obtained by contacting the referring physician, examination by one of our two Mohs surgeons, or by contacting the patient or his or her family. RESULTS: After a median follow-up of 58.0 months (214.3 patient-years), there was one recurrence. This patient was a 56-year-old woman with five prior recurrences before MMS. Six patients were decreased of other causes during the study. CONCLUSIONS: MMS using frozen and rush permanent sections resulted in a 97% cure rate for LM and LMM. Because MMS minimizes the removal of normal tissue, and the cure rate exceeds that of conventional therapies, the authors recommend this technique for the treatment of LM and LMM.

Successful treatment of lentigo maligna and lentigo maligna melanoma with Mohs' micrographic surgery aided by rush permanent sections.

BACKGROUND: Lentigo maligna (LM) is a pigmented neoplasm on sun-exposed skin of elderly patients. LM slowly increases in size and may become lentigo maligna melanoma (LMM), a potentially fatal malignancy. Complete excision is the treatment of choice. Mohs' micrographic surgery (MMS) with frozen and permanent sections may be used for complete eradication of the lesion, while sparing as much normal tissue as possible. The authors studied the efficacy of MMS for the treatment of LM and LMM. METHODS: Between 1985 and 1992, 45 patients with LM (26) and LMM (19) were treated with MMS. The authors' technique was to use examination of frozen sections and rush permanent sections (prepared and read within 24 hours). Positive frozen sections warranted further excision. For negative or equivocal frozen sections, surgery was interrupted until the examination of permanent sections was performed. RESULTS: All 45 patients were free of local disease and evidence of metastases at an average of 29.2 months (range, 4-81 months) after therapy. CONCLUSIONS: MMS aided by rush permanent sections yielded a prolonged disease free survival for all 45 patients with LM or LMM. Because the MMS technique minimizes the removal of normal tissue, and the local cure rate in this study was superior to that reported for conventional surgery, the authors recommend this technique for the treatment of LM and LMM.

In transit from physician to manager--Part II.

In the March-April 1992 issue of Physician Executive, the authors described the six transitions that are required for a successful management career. In the second part of the two-part article, the authors describe some of the obstacles to successful transitions that were disclosed in their research.

In transit from physician to manager--Part I.

Physicians are finding themselves in increasing numbers in significant management roles. Physician managers interviewed about their experiences in changing careers identified six critical transitions, three involving psychological adjustments and three requiring development of new skills. A framework is developed in this two-part article that relates career events that trigger transitions, the transitions themselves, and the obstacles that can hinder or block success. The challenges that physicians encounter in management are similar to those faced by other professional groups, and the chances of successful transition can be improved by individual and organizational actions.

Why physician managers fail--Part Two.

In this second part of the authors' two-part article, they continue with the list of flaws that can cause failure for a physician manager and offer some suggestions for avoiding or overcoming potentially destructive flaws. The authors' findings are based on interviews with a sample of 14 physician executives and on comments received from attendees at workshops of the American College of Physician Executives.

Secrets of management success.

Research has shown that certain characteristics set successful managers apart from their less successful colleagues. Research that is just beginning shows that most of those characteristics also set successful physician executives apart. This article is based on presentations at the College's 1989 National Conference in Washington, D.C., and introduces concepts that will be reported on in more detail in upcoming issues of Physician Executive.

Simple computational model of image correlation by four-wave mixing in photorefractive media.

A simple systems-oriented model of image correlation by nondegenerate four-wave mixing in photorefractive media is discussed, and its computational implementation is described. The model is based on a linear-incomplex modulation index formulation and is capable of describing the correlation product in a wide range of experimental conditions. Bragg matching effects on the test and reference images are explicitly included. The comparison of calculated results with experimental results is excellent, and a discussion of higher-order theories of the photorefractive effect is given. The model is currently being used to optimize the performance of experimental correlators.

Bullous pemphigoid and Hashimoto's thyroiditis.

Both bullous pemphigoid (BP) and Hashimoto's thyroiditis (HT) are suspected of being autoimmune disorders. Each disorder has been reported with other diseases associated with autoimmune phenomena. Thyroid disorders have been reported with BP, but never well documented HT with thyroid antibodies. We report a patient with hypothyroidism due to HT who subsequently developed BP. The importance of this association is discussed, particularly as it relates to autoimmunity.