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Biomedical subjects

K J Roberts

Publications and source records attributed to K J Roberts.

13 recordsLinked to original sources
PubMed2005

Simulation of energetic stability of facetted l-glutamic acid nanocrystalline clusters in relation to their polymorphic phase stability as a function of crystal size.

A molecular modeling approach is used to study the stability of different polymorphic forms of l-glutamic acid through building and optimizing molecular clusters of different sizes and shapes with the latter corresponding to the predicted crystal growth morphologies. The results reveal that the initially nucleating (according to Oswald rule) metastable (alpha) form is the more energetically stable form at small cluster sizes of ca. 200 molecular units, whereas the stable (beta) form is more stable when the cluster size is larger.

Algorithms↗
PubMed2005

Understanding the polymorphic behavior of sibenadet hydrochloride through detailed studies integrating structural and dynamical assessment.

Three polymorphs of sibenadet hydrochloride (AR-C68397AA, Viozan) have been shown to exist at ambient temperature and have been characterized. Each undergoes a solid-state transition to a common high temperature form, which melts at approximately 220 degrees C. X-ray powder diffraction (XRPD) indicates that Polymorphs I and II share a similar layered structure not exhibited by Polymorph III. All three ambient temperature polymorphs show evidence of varying degrees of dynamic disorder of the terminal phenyl group as shown by solid-state NMR spectroscopy. Furthermore, the carbons alpha to the ether link also undergo different rates of mobility in Polymorphs I and II. This variation in the extent of dynamic disorder results in an alteration in the short-range structure resulting in distinct polymorphs. Polymorph I is the thermodynamically stable form at room temperature as indicated by solution calorimetry and assessment by thermodynamically driven solution mediated phase transition studies. The present study aims to address the types of discriminatory data required to make a clear distinction between physical forms and define, unequivocally, the presence of polymorphism.

Adrenergic beta-2 Receptor Agonists↗
PubMed2001

Sodium phenoxyacetate hemihydrate.

The structure of the hemihydrate of sodium phenoxyacetate, Na(+) x C(8)H(7)O(3)(-) x 0.5H(2)O, has been redetermined at low temperature (160 K). The structure consists of ribbons containing octahedral NaO(6) units, and half of the Na(2)O(2) squares within the ribbon are bridged by water molecules which lie across twofold rotation axes in C2/c. The phenyl substituents lie on the outside of the ribbon.

Journal Article↗
PubMed2001

Interatomic potential parameters for potassium tetrachlorozincate and their application to modelling its phase transformations.

An empirical fitting procedure is applied to derive interatomic potential parameters for a model phase transition system, namely potassium tetrachlorozincate (K(2)ZnCl(4)). The derived potential is found to reliably model the known crystallographic structure for the ferroelectric and paraelectric phases of this compound. Potential transferability is demonstrated by applying the parameters derived to the optimization of the known molecular structure for a similar inorganic system (rubidium tetrachlorozincate).

Journal Article↗
PubMed2001

Sodium hydrogen bis(phenoxyacetate).

In the title compound, Na(+) x H(+) x [2C(8)H(7)O(3)](-), the anion contains a short Speakman-type hydrogen bond [O...O = 2.413 (2) A]. The anions and the Na atoms lie across twofold axes.

Journal Article↗
PubMed2000

Barriers to antiretroviral medication adherence in HIV-infected women.

Little is known about the barriers which women living with HIV/AIDS encounter that impede their adherence to antiretroviral medication regimens. Yet in order to design effective interventions to improve women's adherence, it is first imperative to identify the factors that contribute to their non-adherence. The purpose of this study was to explore, from HIV-infected women's own perspectives, the barriers they faced in adhering to combination antiretroviral therapies. Twenty HIV-infected women were asked to keep a personal journal for a period of one month. In the journals, women wrote about what their lives were like while taking antiretroviral medications. Line-by-line open coding was done to identify major ideas and themes within the journal entries. Results showed that women faced six main barriers to adherence, those related to: (1) medication regimens, (2) side effects, (3) social relationships, (4) medication beliefs, (5) daily schedules, and (6) body weight. The findings underscore the difficult nature of the antiretroviral regimens and illuminate the daily obstacles women face in adhering to therapy. Interventions that target women's unique barriers are needed to improve adherence to antiretroviral medication regimens.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Barriers to and facilitators of HIV-positive patients' adherence to antiretroviral treatment regimens.

HIV-positive patients must strictly adhere to antiretroviral regimens for the medications to work properly. Little, however, is known about the obstacles that patients face in adhering to the regimens or what, if anything, helps patients to adhere. The goals of the project were to describe, from HIV-positive patients' own perspectives, the barriers they face in adhering to antiretroviral regimens and the strategies they use to maximize their adherence. Five main barriers (forgetfulness, social/physical environment, complexity of the regimens, medication side effects, and inadequate patient knowledge) to adherence and six main facilitators (mechanical devices, "making a commitment," "routinizing," health beliefs, social support, and professional support) emerged from the data. Patients may overcome some of these barriers by receiving better health education about the need for adherence, professional and lay support for their efforts, and mechanical devices such as alarm clocks and medi-sets. Other barriers, however, such as the complexity of the medications, highlight the need for simplified antiretroviral regimens.

Adult↗
PubMed2000

Barriers to antiretroviral adherence among HIV-infected adults.

Success of highly active antiretroviral therapies (HAART) relies on HIV-infected patients being able to adhere to complicated treatment regimens for extremely long periods of time. Four focus groups with patients taking antiretrovirals (N = 39) were conducted to: (1) determine what strategies facilitate successful adherence; (2) determine what barriers prevent adherence; and (3) investigate the health-care provider and patient relationship and how it may impact adherence. Quantitative and qualitative information was gathered. Participants were prescribed an average of 15 pills per day (M = 14.7, SD = 6.3, range 4 to 36). Findings from the quantitative data revealed that the three strategies used most often to aid adherence were: carrying special containers for medication; having a health-care provider explain or clarify medication requirements; and carrying food and water for adherence to special instructions. The most difficult barriers for patients were sleeping through dose time, problems in following special instructions, and changes in daily routines. From the qualitative data, four main categories of barriers and aids to adherence emerged: patient characteristics, the health-care provider-patient relationship, the health-care system, and issues related to the medication regimen. Barriers related to the health care provider-patient relationship included patient satisfaction with their provider, as well as quality of communication with the provider. In addition, health-care system barriers caused difficulty in maintaining adherence. Implications for patient as well as provider interventions are discussed.

Adult↗
PubMed2000

Physician beliefs about antiretroviral adherence communication.

Adherence to antiretroviral regimens is thought to be imperative for HIV-positive patients. However, little is known about health care professionals' willingness to discuss adherence with patients, nor what barriers, if any, may impede their adherence communication. The aims of the study were to examine physicians' beliefs regarding: (1) the efficacy of adherence communication, (2) the barriers which impede such communication, and (3) their roles and responsibilities regarding adherence communication. Semi-structured interviews were conducted with 15 physicians who specialize in providing care to HIV-positive patients. Results showed that most physicians believed that communicating with patients about adherence issues was important, even though doing so may not have an immediate impact on patients' behaviors. Physicians believed that adherence communication was a good use of their time and fell within their role as a primary care professional. However, time constraints were cited as a barrier to performing adherence communication, indicating that physicians may do less communicating about adherence than may be optimal if they are burdened with other tasks. Results highlight the need to develop innovative strategies, such as the use of multi-disciplinary adherence teams, to ensure that each HIV-positive patient receives the optimal amount of information about and support for adherence.

Adult↗
PubMed1999

Adherence communication: a qualitative analysis of physician-patient dialogue.

OBJECTIVE: To explore how HIV/AIDS care physicians communicate with HIV-positive patients about the need for adherence to antiretroviral treatment regimens. DESIGN: Semi-structured, face-to-face interviews, a qualitative research method. SETTING: A comprehensive, multidisciplinary, HIV/AIDS practice at San Francisco General Hospital. PARTICIPANTS: Fifteen physicians, most of whom (73%) were board certified in internal medicine and/or infectious diseases; all were involved in HIV continuity care. RESULTS: Most physicians engaged in both pre- and post-prescription phases of adherence communication with their patients. During the pre-prescription phase, physicians made decisions about offering prescriptions to patients, often based on their beliefs about the patient's likelihood of adhering to therapy. During the post-prescription phase, physicians asked patients questions about if/how they were adhering to the regimens. Physicians' practices, such as the length of time spent in the pre-prescription phase, the timing of the 'check-ins' in the post-prescription phase, and the overall content of both phases, varied significantly. CONCLUSIONS: Physicians have diverse ways of communicating with patients regarding adherence to antiretroviral medications. The effect of such communication on treatment outcomes needs to be assessed; however, the potential benefit suggests that training programs should be developed to improve physicians' skills in this area. Further studies should be done to assess how generally applicable these findings are to other groups of physicians.

Adult↗
PubMed1999

Facilitators and barriers to use of the female condom: qualitative interviews with women of diverse ethnicity.

Women in the United States, particularly African-Americans and Hispanics, are at increased risk for HIV. The female condom now offers women a potentially important option for HIV prevention, yet few efforts have been made to increase its use. To elucidate strategies to promote the use of the female condom, we conducted in-depth interviews with 62 women recruited from the four major racial/ethnic groups of the U.S. (African-American, Asian-American, Hispanic, and white). Subject recruitment took place at a family planning clinic in San Francisco during 1996-97. We identified four major types of facilitators and barriers to use of the female condom: mechanical, psychosexual, interpersonal, and situational. Specifically, the mechanical facilitators and barriers included positive and negative aspects of the device, and difficulty with insertion. The psychosexual factors were female empowerment, more options for contraception and disease prevention, discomfort with vaginal insertion, and condom use norms. The interpersonal factors included: enhanced communication, relationship status, partner preferences, and partner objections. Finally, the situations that made women disinclined to use the device were: no access to the female condom when having sex and using other forms of contraceptives. The implications of these findings for HIV prevention and future research are discussed.

Adolescent↗
PubMed1997

Modeling the crystal morphology of alpha-lactose monohydrate.

Molecular modeling techniques using attachment energy calculations have been applied, for the first time to our knowledge, to simulate the morphology of an organic hydrate: alpha-lactose monohydrate. Calculation of the strong intermolecular forces using the atom-atom approximation and the potential parameters of Nemethy et al. (Némethy, G.; Pottle, M. S.; Scheraga, H. A. J. Phys. Chem. 1983, 87, 1883-1887) reveals the crystallization to be dominated by intermolecular interactions between lactose molecules rather than lactose-water interactions, suggesting that water of hydration plays a space-filling role in the growth process. The simulated crystal shows a tomahawk-like morphology with the polar effect of the monoclinic space group P21 correctly reproduced by the occurrence of only one of the [010] forms. Confrontation of these results with experimental work of our own, involving crystals precipitated from aqueous solutions at various degrees of undercooling examined by scanning electron microscopy, and that of Visser and Bennema (Visser, R. A.; Bennema, P. Neth. Milk Dairy J. 1983, 37,109-137), who assigned faces to a crystal, gives good agreement, suggesting the suitability of the force field and atom-atom approaches to model the crystallization of organic hydrates.

Crystallography, X-Ray↗