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J Fenwick

Publications and source records attributed to J Fenwick.

At least 19 recordsLinked to original sources
PubMed2005

The helical tomotherapy thread effect.

Inherent to helical tomotherapy is a dose variation pattern that manifests as a "ripple" (peak-to-trough relative to the average). This ripple is the result of helical beam junctioning, completely unique to helical tomotherapy. Pitch is defined as in helical CT, the couch travel distance for a complete gantry rotation relative to the axial beam width at the axis of rotation. Without scattering or beam divergence, an analytical posing of the problem as a simple integral predicts minima near a pitch of 1/n where n is an integer. A convolution-superposition dose calculator (TomoTherapy, Inc.) included all the physics needed to explore the ripple magnitude versus pitch and beam width. The results of the dose calculator and some benchmark measurements demonstrate that the ripple has sharp minima near p=0.86(1/n). The 0.86 factor is empirical and caused by a beam junctioning of the off-axis dose profiles which differ from the axial profiles as well as a long scatter tail of the profiles at depth. For very strong intensity modulation, the 0.86 factor may vary. The authors propose choosing particular minima pitches or using a second delivery that starts 180 deg off-phase from the first to reduce these ripples: "Double threading." For current typical pitches and beam widths, however, this effect is small and not clinically important for most situations. Certain extremely large field or high pitch cases, however, may benefit from mitigation of this effect.

Algorithms↗
PubMed2002

Time from insemination to first cleavage predicts developmental competence of human preimplantation embryos in vitro.

BACKGROUND: The absence of reliable markers for the identification of viable embryos for transfer at the early cleavage stage is likely to contribute to the generally low implantation rates and high incidence of multiple gestation in IVF treatment. In this study, we investigate the relationship between timing of first cleavage and the incidence of blastocyst formation in vitro. METHODS: Couples (n = 70) with at least one embryo remaining after transfer were included in the analyses. All embryos (n = 579) were examined for early cleavage at 25 h after insemination. Following embryo transfer, the remaining embryos (n = 426) were cultured until day 7 of development, and assessed for blastocyst formation. RESULTS: Eighty-five embryos (14.7%) cleaved to the 2-cell stage within 25 h of insemination; 26 of these were selected for transfer on day 2. Of the 59 embryos remaining in culture, 19 (32.2%) developed to the blastocyst stage; this was a significantly higher number than was observed in embryos (61/367; 16.6%) that failed to cleave within 25 h of insemination (P < 0.01). Within these two groups of embryos the proportion of hatched blastocysts was 11/59 (18.6%) and 26/367 (7.1%) respectively (P < 0.005). CONCLUSIONS: These findings indicate that early cleavage is indicative of increased developmental potential in human embryos and may be useful as an additional criterion in the selection of embryos for transfer.

Adult↗
PubMed2001

'They've forgotten that I'm the mum': constructing and practising motherhood in special care nurseries.

Little sociological research has sought to investigate the ways in which women with hospitalized newborn infants construct and practice motherhood. This article seeks to address this lacuna, using data from a qualitative research project based in two Australian neonatal nurseries. Thirty-one mothers of hospitalized newborns and 20 neonatal nurses were interviewed, and other data were obtained via observations of the nurseries, tape-recorded verbal interactions between parents and nursery staff and casual conversations with mothers and nurses. The data revealed that while the mothers' and nurses' discourses on what makes a 'good mother' in the context of the neonatal nursery converged to some extent, there were important differences. The mothers particularly emphasized the importance of physical contact with their infants and breastfeeding, while the nurses privileged presence in the nursery and willingness to learn about the infant's condition and treatment. There was evidence of power struggles between the mothers and nurses over the handling and treatment of the infants, which had implications for how the mothers constructed and practised motherhood. The mothers attempted to construct themselves as 'real mothers', which involved establishing connection with their infants and normalizing them. In time, many of the mothers sought to position themselves as the 'experts' on their infants. For their part, the nurses attempted to position themselves as 'teachers and monitors of the parents', 'protectors of the infants' and 'experts' by virtue of their medical training and experience. Differences in defining the situation resulted in frustration, resentment and anger on the part of the mothers and disciplinary and surveillance actions on the part of many of the nurses, both covert and overt. The nurses' attitude to and treatment of the mothers was integral in the development of the mothers' relationship with their infants in the nurseries, and this influence extended beyond discharge of the infants.

Child, Hospitalized↗
PubMed2001

'Chatting': an important clinical tool in facilitating mothering in neonatal nurseries.

AIM: This paper explores the use of 'chat' or 'social talk' as an important clinical tool that can assist nurses achieve family-centred care in neonatal nurseries. BACKGROUND: The study was undertaken to increase knowledge of women's experiences of mothering in the neonatal nursery and the relationship they share with nurses. METHOD: The discussion presented is elicited from a grounded theory analysis of over 60 hours of interview data with 28 women, a thematic analysis of 50 hours of interviews with 20 nurses and a content analysis of 398 tape-recorded interactions between nurses and parents. FINDINGS: The analysis identifies the importance of the nurse-mother relationship and demonstrates that it is both the context and method by which nursing care is delivered. We found the verbal exchanges that take place between nurse and mother influence a woman's confidence, her sense of control and her feelings of connection to her infant. It appears from the data that the nurse's ability to effectively 'engage' the mother is dependent on the use of language that expresses care, support and interest in parents. CONCLUSIONS: The data suggests that 'chatting' is the strategy and the process through which positive interactions are initiated, maintained and enhanced. This study confirms that nurses' language acts as a powerful clinical tool that can be used to assist parents in gaining confidence in caring for their infants and in becoming 'connected' to infants resident in nurseries.

Adult↗
PubMed2001

Estimation of glomerular filtration rate in cancer patients.

The frequent need to obtain an estimate of renal function in cancer patients, not least for targeting carboplatin dose, has led to a number of approaches to estimate glomerular filtration rate (GFR). This study aimed to develop a simple and reliable method to estimate GFR using readily-available patient characteristics. Data from 62 patients with estimates of 51Cr-EDTA clearance were analysed to determine the most appropriate formula relating this method of measuring GFR to patient characteristics. The population pharmacokinetics of 51Cr-EDTA were analysed using NONMEM to evaluate the influence of each covariate. The formulae derived were then validated using a further 38 patients and compared with those obtained using existing formulae. 51Cr-EDTA clearance (GFR) was positively related to Dubois surface area, negatively related to age, and inversely related to serum creatinine (SCr). Females had lower 51Cr-EDTA clearance than males. The enzymatic method of SCr assay gave more reliable results than the Jaffe colorimetric method. A measure of creatine kinase significantly improved the estimation of GFR. The new formula produced estimates of GFR which were less biased (Mean Prediction Error = -3%) and more precise (Mean Absolute Prediction Error = 12%) than Cockcroft and Gault (-8% and 16%) or Jelliffe (-15% and 19%) estimates. The formulae developed here can be used to provide reliable estimates of GFR, particularly in regard to targeted dosing of carboplatin.

Adolescent↗
PubMed2001

Struggling to mother: a consequence of inhibitive nursing interactions in the neonatal nursery.

This paper reports on one aspect of a grounded theory study of women's experiences of mothering in the nursery. Over 60 hours of interview data with 28 Australian women were analyzed. The analysis revealed that mothering in the nursery was a three-way interaction. "Struggling to mother" was the label given to the major category that represented how women responded to unsatisfactory nursing encounters. The findings illuminate how inhibitive nursing interactions relegate women to the periphery of care and engender an array of negative emotional responses that leave women feeling inconsequential to the welfare of their infant. Ultimately this has implications for how women take up their role as mothers in the nursery and for their sense of confidence, competence, and connection with their infant.

Australia↗
PubMed2000

Ligament mechanics during three degree-of-freedom motion at the acromioclavicular joint.

The development of effective treatment and reconstruction procedures for injuries to the soft tissues around the acromioclavicular (AC) joint relies on a comprehensive understanding of overall joint function. The objective of this study was to determine the magnitude and direction of the in situ forces in the AC capsular and coracoclavicular ligaments as well as the resulting joint kinematics during application of three external loading conditions while allowing three degree-of-freedom joint motion. A robotic/universal force-moment sensor testing system was utilized to determine the in situ forces in the soft tissue structures and the resulting joint kinematics. The clavicle translated 5.1+/-2.0, 5.6+/-2.2, and 4.2+/-1.9 mm during application of a 70 N load in the anterior, posterior, and superior directions, respectively, representing almost a 50% increase over previous studies using similar load magnitudes. In response to an anterior load, the magnitude of in situ force in the superior AC ligament (35+/-18 N) was found to be greater (p<0.05) than the force in the trapezoid and conoid ligaments. In contrast, the magnitude of in situ force in the conoid (49+/-22 N) was significantly greater (p<0.05) than all other ligaments in response to a superior load. Additionally, the directions of the force vector representing the conoid and trapezoid were different, being located in opposing quadrants of the posterior axis of the scapula with this loading condition. Our data suggest that the kinematic constraints placed on the AC joint during loading affect the resulting joint motion and that the magnitude and direction of force in each ligament are affected by the coupled motions that occur. Based on the differences in magnitude and direction of the in situ force in the coracoclavicular ligaments with each loading condition, surgical procedures should reconstruct these ligaments in a more anatomical manner or treat them separately to prevent joint degeneration.

Acromioclavicular Joint↗
PubMed1999

A story: nursing-damaged lives.

This paper presents a story that captures forever a 'difficult', 'horrible' but in many respects totally 'normal' nursing moment. It is a short story of only one person's reality. On that fateful night in which many lives were changed forever, there were, of course, many realities, all of which hold their own truth. This tale is offered in the spirit of sharing and in the hope that others may find it useful. I believe that 'story telling' allows us to revisit and review our practice. In doing so, stories facilitate the discovery of nursing knowledge and the self. Ultimately this contributes to the development of expert practice. Nursing stories, then, become an excellent medium for nursing inquiry, from both an academic and a clinical perspective.

Accidents, Traffic↗
PubMed1999

Activities and interactions in level II nurseries: a report of an ethnographic study.

This article reports an ethnographic study that examines the context and nature of the interactions between health professionals and parents in two Australian level II nurseries: 724 observations were recorded over an 18-week period. Analysis revealed that although the presence of mothers in the nursery was high, registered nurses remain the primary caretakers of the infants. The interactions between registered nurses and mothers were found to be action- or task-oriented with communication largely being described as "instrumental." The results of this pilot work suggest that the emphasis of clinical practice in level II nurseries remains focused on caring for the infant and teaching the mother. This is in contrast to the current body of literature that identifies the need for a family-centered approach to care that aims to support parents as they develop confidence, attach to their baby, and become skilled in providing care themselves.

Adult↗
PubMed1999

Carboplatin and paclitaxel, alone and in combination: dose escalation, measurement of renal function, and role of the p53 tumor suppressor gene.

In this pharmacokinetic and dose-escalation study of the carboplatin/paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) combination, patients were randomly assigned to receive paclitaxel either as a 1-hour or a 3-hour infusion. The 1-hour infusion was feasible, with maximum tolerated doses similar to those previously reported for a 3-hour infusion. Using patients' age, height, plasma creatinine, and plasma creatine kinase provided an improved estimate of the glomerular filtration rate compared with the more traditional creatinine-based formulas according to population analysis of data derived from glomerular filtration rate estimates performed by an isotope method. Studies of the p53 gene sequence of ovarian tumors at diagnosis suggest that p53 mutations are a potent predictor of response to subsequent treatment with carboplatin.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Mothering and midwifery: sometimes a challenge.

This paper attempts to present two levels of argument. Firstly it argues that the use of story, in its entirety, is a valid, relevant and useful tool for informing personal and professional knowing. The second level of debate is elicited by the story itself and the discourse surrounding the challenges of implementing continuity of midwifery care models within the mainstream maternity care system. The author hopes that the telling of the story provides a window through which others can share her experience. It is argued that 'identification' with the challenges involved in implementing innovative models of care is an important and vital step in the process, if these models are to begin, survive and achieve their aim of providing women-centred health care.

Adaptation, Psychological↗
PubMed1998

Effects of profound suppression of luteinizing hormone during ovarian stimulation on follicular activity, oocyte and embryo function in cycles stimulated with purified follicle stimulating hormone.

The effects of profound suppression of circulating luteinizing hormone (LH) during the follicular phase of in-vitro fertilization cycles were explored in normal women during treatment with a gonadotrophin-releasing hormone analogue and exogenous purified follicle stimulating hormone. Ovarian responses to treatment and the capacity of supernumerary embryos to undergo blastocyst formation were examined in groups of patients defined by the concentration of plasma LH in the mid-follicular phase. Concentrations < or = 0.5 IU/I diagnosed the group with profoundly suppressed LH (<LH, n = 20), which was compared with the remaining patients (nLH, n = 41). The <LH group showed lower oestradiol concentrations at human chorionic gonadotrophin administration, while the total follicular development estimated by the total follicular diameters was similar in both groups. The oestradiol secreted per follicle, estimated by the circulating concentration per mm total follicular diameter, was significantly lower in the <LH group. The combined effects of a trend to lower yield of oocytes (not significant) and a lower fertilization rate (not significant) resulted in a significantly reduced quantity of embryos available for cryopreservation after the fresh transfer. Supernumerary embryos were cultured for 7 days to determine blastocyst development rates, and the degree of LH suppression made no difference to embryo developmental competence (nLH, 23%; <LH, 27%), or the rates of blastocyst formation. The group of patients with profoundly suppressed mid-follicular phase LH showed a reduced yield of oocytes and embryos which resulted in significantly fewer embryos available for cryopreservation. However, the developmental potential of those embryos, represented by the ability to form blastocysts in vitro, was unaffected.

Adult↗
PubMed1998

Diastolic filling in human severe sepsis: an echocardiographic study.

OBJECTIVE: To determine if nonsurvivors have a more abnormal pattern of left ventricular relaxation than survivors with severe sepsis. DESIGN: Prospective, observational, cohort study. SETTING: Intensive care unit in a university-affiliated tertiary care hospital. PATIENTS: Twenty-four adults with severe sepsis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Baseline clinical and hemodynamic variables, Acute Physiology and Chronic Health Evaluation (APACHE) II scores and Doppler echocardiographic mitral inflow pattern (analyzed for normalized peak early filling rate [E/VTI, systolic volumes/sec], deceleration time [msec], and early to atrial filling velocity ratio [E/A]). There were seven deaths. The patients did not differ in baseline demographics, inotropic infusions, hemodynamic measurements or ventilatory settings or variables. Nonsurvivors had a more abnormal pattern of left ventricular relaxation (E/VTI, 4.7 [range 3.8 to 5.8] vs. 5.8 [range 3.8 to 8.9], p= .04; deceleration time, 235 [range 209 to 367] vs. 182 [range 155 to 255], p = .002). E/A showed a nonsignificant trend in the same direction (0.9 [range 0.8 to 1.6] vs. 1.2 [range 0.7 to 1.9], p = .12). In a multivariate analysis, deceleration time (p< .004) and APACHE II score (p < .02) were the only independent predictors of mortality. CONCLUSION: Severe sepsis nonsurvivors have a more abnormal echocardiographic pattern of left ventricular relaxation than survivors.

APACHE↗
PubMed1998

HONC measures in 4- to 6-year-old children. Horii Oral Nasal Coupling Index.

OBJECTIVE: To collect normative data using Horii's Oral Nasal Coupling Index (HONC) from 4- to 6-year-old children without cleft palate to be used in the evaluation of young children with cleft palate. In addition, to determine whether HONC values in children are similar to those of adults and thus show that the HONC ratio successfully normalizes nasal accelerometric signals across age, gender, and vocal intensity. DESIGN: Measurement of accelerometric and acoustic signals from novel nasal and nonnasal utterances, which the children repeated after the experimenter. Measurements also included four sustained [m] productions, which were used to calibrate correction factors used to equate nasal and oral signals during a sustained [m] production. SETTING: Laboratory at a state university. PARTICIPANTS: Ten girls and 10 boys, aged 4 to 6 years, with normal speech, language, and hearing. RESULTS: Differences of 13 dB (HONC) were found to separate nasal from nonnasal sentences. No significant difference in HONC score was found across gender for nasal/nonnasal sentences and [m] productions. The correction factors generated during [m] calibration procedures did not differ between girls and boys. CONCLUSIONS: Horii Oral Nasal Coupling Index differences between nasal and nonnasal utterances appear to be valid and reliable measures in both children and adults for detection of disorders of nasal resonance.

Acceleration↗
PubMed1997

Detection of mosaic and non-mosaic chromosome abnormalities in 6- to 8-day old human blastocysts.

A reliable technique has been developed for the production of good quality G-banded chromosome preparations from 6- to 8-day-old human blastocysts (20-800 cell stage) from an in vitro fertilization programme. The technique involves a thymidine cell division synchronization step to reduce the exposure time to colcemid, in conjunction with a simple 70% acetic acid disaggregation procedure to produce discrete metaphases for analysis. Of 105 blastocysts processed by this technique, 9 were lost during handling and 10 showed no dividing cells. The remaining 86 produced useful separate metaphases with a mean mitotic activity of 6.5%. A full G-banded karyotype was obtained from 1-6 cells in 55 blastocysts (64%), incomplete G-banded analysis but with full information of ploidy was obtained from 18 blastocysts (21%), with 13 (15%) producing no useful cytogenetic results. Abnormalities observed included polyploidy, diploid/polyploid mosaicism, non-mosaic trisomy 16 (2 cases), 46,Xdel(X)-(q21)/46,XX (1 case) and several single cells with trisomies or structural anomalies in otherwise normal blastocysts. Variable levels of structural chromosome damage, with apparent interchanges, chromosome branching and anomalous chromatid pairing were also seen.

Aneuploidy↗
PubMed1997

Albumin is not suitable as a marker of bronchoalveolar lavage dilution in interstitial lung disease.

We have investigated the origin of raised bronchoalveolar lavage (BAL) albumin levels in interstitial lung diseases (ILDs), and the hypothesis that acute flux during BAL might contribute to the elevated levels of albumin in samples from ILD patients. Total albumin concentrations were measured in three separately aspirated 60 mL aliquots of BAL in 12 ILD patients and seven control subjects, and previous work indicating that BAL albumin levels may be raised in ILD was confirmed. In addition, the extent of acute flux from the circulation was investigated using 1.48 MBq of 125I-radiolabelled human serum albumin injected intravenously shortly before the procedure. It was found that acute albumin flux occurred in only a minority of the ILD patients (4 out of 12) and control subjects (3 out of 7). These results indicate that the elevated levels of plasma proteins, such as albumin, documented in BAL aspirates from ILD patients are not an artefact of the BAL procedure related to increased vascular permeability, and that this finding is more likely to be related to the effects of chronic inflammatory changes in the lung due to the underlying disease. The work confirms that albumin is unsuitable as a denominator for the normalization of bronchoalveolar lavage solute results, since levels can vary, both as a result of acute flux and, more frequently, because of disease activity.

Adult↗