Buoyancy-driven, rapid exhumation of ultrahigh-pressure metamorphosed continental crust

Preservation of ultrahigh-pressure (UHP) minerals formed at depths of 90–125 km require unusual conditions. Our subduction model involves underflow of a salient (250 ± 150 km wide, 90–125 km long) of continental crust embedded in cold, largely oceanic crust-capped lithosphere; loss of leading portions of the high-density oceanic lithosphere by slab break-off, as increasing volumes of microcontinental material enter the subduction zone; buoyancy-driven return toward midcrustal levels of a thin (2–15 km thick), low-density slice; finally, uplift, backfolding, normal faulting, and exposure of the UHP terrane. Sustained over ≈20 million years, rapid (≈5 mm/year) exhumation of the thin-aspect ratio UHP sialic sheet caught between cooler hanging-wall plate and refrigerating, downgoing lithosphere allows withdrawal of heat along both its upper and lower surfaces. The intracratonal position of most UHP complexes reflects consumption of an intervening ocean basin and introduction of a sialic promontory into the subduction zone. UHP metamorphic terranes consist chiefly of transformed, yet relatively low-density continental crust compared with displaced mantle material—otherwise such complexes could not return to shallow depths. Relatively rare metabasaltic, metagabbroic, and metacherty lithologies retain traces of phases characteristic of UHP conditions because they are massive, virtually impervious to fluids, and nearly anhydrous. In contrast, H2O-rich quartzofeldspathic, gneissose/schistose, more permeable metasedimentary and metagranitic units have backreacted thoroughly, so coesite and other UHP silicates are exceedingly rare. Because of the initial presence of biogenic carbon, and its especially sluggish transformation rate, UHP paragneisses contain the most abundantly preserved crustal diamonds.

Circulation of core collection monographs in an academic medical library

Academic medical librarians responsible for monograph acquisition face a challenging task. From the plethora of medical monographs published each year, academic medical librarians must select those most useful to their patrons. Unfortunately, none of the selection tools available to medical librarians are specifically intended to assist academic librarians with medical monograph selection. The few short core collection lists that are available are intended for use in the small hospital or internal medicine department library. As these are the only selection tools available, however, many academic medical librarians spend considerable time reviewing these collection lists and place heavy emphasis on the acquisition of listed books. The study reported here was initiated to determine whether the circulation of listed books in an academic library justified the emphasis placed on the acquisition of these books. Circulation statistics for “listed” and “nonlisted” books in the hematology (WH) section of Indiana University School of Medicine's Ruth Lilly Medical Library were studied. The average circulation figures for listed books were nearly two times as high as the corresponding figures for the WH books in general. These data support the policies of those academic medical libraries that place a high priority on collection of listed books.

Assessment of Customer Service in Academic Health Care Libraries (ACSAHL): an instrument for measuring customer service*†

Objectives: In a pilot study, the library had good results using SERVQUAL, a respected and often-used instrument for measuring customer satisfaction. The SERVQUAL instrument itself, however, received some serious and well-founded criticism from the respondents to our survey. The purpose of this study was to test the comparability of the results of SERVQUAL with a revised and shortened instrument modeled on SERVQUAL. The revised instrument, the Assessment of Customer Service in Academic Health Care Libraries (ACSAHL), was designed to better assess customer service in academic health care libraries.

Providing health information to the general public: a survey of current practices in academic health sciences libraries*

A questionnaire was mailed to 148 publicly and privately supported academic health sciences libraries affiliated with Association of American Medical Colleges (AAMC)–accredited medical schools in the United States and Canada to determine level of access and services provided to the general public. For purposes of this study, “general public” was defined as nonaffiliated students or health care professionals, attorneys and other nonhealth-related professionals, patients from affiliated or other hospitals or clinics, and general consumers. One hundred five (71%) libraries responded. Results showed 98% of publicly supported libraries and 88% of privately supported libraries provided access to some or all of the general public. Publicly supported libraries saw greater numbers of public patrons, often provided more services, and were more likely to circulate materials from their collections than were privately supported libraries. A significant number of academic health sciences libraries housed a collection of consumer-oriented materials and many provided some level of document delivery service, usually for a fee. Most allowed the public to use some or all library computers. Results of this study indicated that academic health sciences libraries played a significant role in serving the information-seeking public and suggested a need to develop written policies or guidelines covering the services that will be provided to minimize the impact of this service on primary clientele.

Monograph use at an academic health sciences library: the first three years of shelf life

Objective: To study the circulation of monographs during the first three years of shelf life at an academic health sciences library.