bluuebunny/crossref_metadata_2025 huggingface dataset:
Detrusor Underactivity: Clinical Features and Pathogenesis of an Underdiagnosed Geriatric Condition
Authors: Taylor John A. , Kuchel George A.
Published: October 2006

Urinary incontinence and other lower urinary tract symptoms exert a major influence on the health and independence of frail older people. Detrusor underactivity (DU) is defined as a contraction of reduced strength and/or duration, resulting in prolonged bladder emptying and/or a failure to achieve complete bladder emptying within a normal time span. DU may influence the clinical presentation and impede the therapy of disorders as common and as disparate as detrusor overactivity, urinary retention, and benign prostatic hyperplasia. Urodynamically, nearly two‐thirds of incontinent nursing home residents exhibit DU. The clinical diagnosis of DU when present alone or in association with other bladder conditions such as detrusor overactivity (detrusor hyperactivity with impaired contractility (DHIC)) is challenging, because symptoms lack adequate precision. A catheterized and increasingly noninvasive ultrasound‐based postvoid residual assessment allows a bedside diagnosis of retention and may suggest the presence of DU in individuals (mostly women) with a low likelihood of bladder outlet obstruction (BOO). Nevertheless, it cannot differentiate primary DU from retention secondary to BOO. The management of individuals with DHIC remains unsatisfactory, because antispasmodic anticholinergic medications may worsen retention, whereas bethanechol does not improve bladder emptying. Human detrusor biopsies reveal axonal degeneration, muscle loss, and fibrosis in DU. Animal studies suggest that multiple risk factors, including retention itself, lack of estrogen, infection, inflammation, and aging, may contribute to DU. Priority areas for future research include efforts to facilitate clinical nonurodynamic diagnosis of probable DU plus translational research designed to address the pathogenesis of this complex multifactorial geriatric syndrome.
Initial Evaluation of a Technique for Complete Cecal Bypass in the Horse
Authors: SYMM WILLIAM A. , NIETO JORGE E. , VAN HOOGMOED LINDA , SNYDER JACK R.
Published: October 2006

Objective— To describe a novel stapling technique for creation of a complete cecal bypass, without ileal transection in horses.

Study Design— Experimental study.

Animals— Four adult horses.

Methods— Through a ventral median celiotomy, jejunocolostomy was made with an intraluminal anastomosis device (ILA‐100) and oversewn with a Cushing pattern to reinforce the staple line. Immediately distal to the anastomosis, 4 rows of staples were applied using a thoracoabdominal stapling device (TA‐90) to occlude the lumen of the distal jejunum and proximal ileum. Necropsy exams were performed at least 60 days after surgery.

Results— No intraoperative complications occurred. Cecal bypass was functional in all horses at necropsy. The most oral staple line across the ileum partially failed in 1 horse; however cecal bypass was functional.

Conclusions— Complete cecal bypass without ileal transection is a viable alternative to traditional methods of complete cecal bypass. Two sets of staple lines across the ileum are recommended. Longer term follow‐up is warranted before clinical use of this technique.

Clinical Relevance— Cecal bypass without ileal transection is technically simple and effectively bypasses the cecum. It also should intuitively require less time and have a reduced risk of contamination compared with complete cecal bypass with ileal transection.
Achieving targets for bone and mineral metabolism: The impact of cinacalcet HCl in clinical practice
Authors: SPIEGEL David M. , CASEY Lynn , BELL Susan , PARKER Michelle , CHONCHOL Michel
Published: October 2006

Achieving the K/DOQI targets for bone and mineral metabolism has proven difficult with the use of vitamin D analogues and phosphate binders. The introduction of cinacalcet HCl provided a new tool with a novel therapeutic mechanism of action. The purpose of this study was to evaluate the effect of the introduction of combination algorithm for managing secondary hyperparathyroidism (SHPT) on phosphorus, calcium, and biointact parathyroid hormone (PTH). The 61 patients who dialyzed in the facility from January 2004 (baseline) and who remained in the facility as of April 2005 (follow‐up) were included in the study. In the baseline period, 37 (61%) of the patients received paricalcitol at some time during the 3‐month observation period. In the follow‐up period, 19% or 31% of the patients received cinacalcet HCl. Of those not receiving cinacalcet HCl, 67% had PTH at or below target, 17% were felt to be noncompliant with oral meds, 7% had low calcium, and 10% either could not get the medication or were not switched to the combination pathway. Compared with the baseline period, the percent of patients who met the PTH target increased from 19.7% to 37.7%, p<0.05. The percent of patients meeting all 4 targets increased from 14.8% to 24.6%, although this did not reach statistical significance. The introduction of cinacalcet HCl into a treatment algorithm for management of SHPT resulted in a significant increase in the percentage of patients achieving the PTH target while maintaining the other mineral metabolism targets.
Review of dialysate calcium concentration in hemodialysis
Authors: TOUSSAINT Nigel , COONEY Patrick , KERR Peter G.
Published: October 2006

The dialysate calcium (Ca) concentration for hemodialysis (HD) patients can be adjusted to manage more optimally the body's Ca and phosphate balance, and thus improve bone metabolism as well as reduce accelerated arteriosclerosis and cardiovascular mortality. The appropriate dialysate Ca concentration allowing this balance should be prescribed to each individual patient depending on a multitude of variable factors relating to Ca load. A lower dialysate Ca concentration of 1.25 to 1.3 mmol/L will permit the use of vitamin D supplements and Ca‐based phosphate binders in clinical practice, with much less risk of Ca loading and resultant hypercalcemia and calcification. Low Ca baths are useful in the setting of adynamic bone disease where an increase in bone turnover is required. However, low Ca levels in the dialysate may also predispose to cardiac arrhythmias and hemodynamically unstable dialysis sessions with intradialytic hypotension. Higher Ca dialysate is useful to sustain normal serum Ca levels where patients are not taking Ca‐based binders or if Ca supplements are not able to normalize serum levels. Suppression of hyperparathyroidism is also effective with dialysate Ca of 1.75 mmol/L, but hypercalcemia, metastatic calcification, and oversuppression of parathyroid hormone are risks. Dialysate Ca of 1.5 mmol/L may be a compromise between bone protection and reduction in cardiovascular risk for conventional HD and is a common concentration used throughout the world. The increase in longer, more frequent dialysis such as short‐daily and nocturnal HD, however, provides another challenge with regard to optimal dialysate Ca levels and higher levels of 1.75 mmol/L are probably indicated in this setting. Difficulties in determining the ideal dialysate Ca occur because of the complex pathophysiology of bone and mineral metabolism in HD patients and there needs to be a balance between dialysis prescription and other treatment modalities. To optimize management of the abnormal Ca balance, other aspects of this disorder need to be more fully clarified and, with evolving medications for phosphate control and treatment of secondary hyperparathyroidism, as well as the emergence of a multitude of different HD regimes, further studies are required to make definitive recommendations. At present, we need to maintain flexibility with HD treatments and so dialysate Ca needs to be individualized to meet the specific requirements of patients by optimizing management of renal bone disease and simultaneously reducing metastatic calcification and cardiovascular disease.
Continuous online monitoring of ionic dialysance allows modification of delivered hemodialysis treatment time
Authors: CHESTERTON Lindsay J. , PRIESTMAN William S. , LAMBIE Stewart H. , FIELDING Catherine A. , TAAL Maarten W. , FLUCK Richard J. , MCINTYRE Christopher W.
Published: October 2006

Considerable intrinsic intrapatient variability influences the actual delivery of Kt/V. The aim of this study is to examine the feasibility of using continuous online assessment of ionic dialysance measurements (Kt/VID) to allow dialysis sessions to be altered on an individual basis. Ten well‐established chronic hemodialysis (HD) patients without significant residual renal function were studied (mean age 65±4.3 [38–81] years, mean length of time on dialysis 66±18 [14–189] months). These patients had all been receiving thrice‐weekly 4‐hr dialysis using Integra® dialysis monitors. Dialysis monitors were equipped with Diascan® modules permitting measurement of Kt/VID. Predicted treatment time required to achieve a Kt/VID≥1.1 (equivalent to a urea‐based method of 1.2) was calculated from the delivered Kt/VID at 60 and 120 min. Treatment time was reprogrammed at 2 hr (ensuring all planned ultrafiltration would be accommodated into the new modified session duration). Owing to practical issues, and to avoid excessively short dialysis times, these changes were censored at no more than±10% of the usual 240‐min treatment time (210–265 min). Data were collected from a total of 50 dialysis sessions. Almost all sessions (47/50) required modification of the standard treatment time: 13/50 sessions were lengthened and 34/50 shortened (mean length of session 232.2±2.5 [210–265] min). A Kt/VID of ≥1.1 was achieved in 39/50 sessions. The difference in mean urea‐based Kt/V poststudy (1.3±0.05 [1.1–1.6]) and mean achieved Kt/VID (1.16±0.02 [0.7–1.37]) was significant (p=0.002). The use of individualized variable dialysis treatment time using online ionic dialysance measurements of Kt/VID appears both practicable and effective at ensuring consistently delivered adequate dialysis.
Tuberculosis in end‐stage renal disease patients on hemodialysis
Authors: ABDELRAHMAN Mohammad , SINHA Ajit Kumar , KARKAR Ayman
Published: October 2006

Recent studies have shown that there is an increase in the incidence of mycobacterium tuberculosis (MBT). This is more prevalent among immune compromised patients (those on dialysis) and recipients of organ transplants. Furthermore, extra‐pulmonary presentation appears to be more common and difficult to diagnose. We aimed in this study to assess and evaluate the presentation of MBT in a retrospective study conducted among 256 hemodialysis (HD) patients where 18 of them were diagnosed and managed for tuberculosis over a 10‐year period between 1990 and 2000. The mean age of the patients was 38 years (21–75 years). The mean interval between the onset of HD and the time of diagnosis was about 24 months (1–120 months). The diagnosis of tuberculosis was made either by isolation of acid‐fast bacilli (AFB), the typical caseating granuloma on biopsy, or by recovery of tubercle bacilli from the culture of the biopsy material. Extra‐pulmonary tuberculosis was more common (77.8%) than pulmonary tuberculosis (22.2%). The various extra‐pulmonary tuberculosis sites noted were cervical lymphadenitis (16.7%), gastrointestinal (16.7%), genitourinary (11.1%), peritonitis (11.1%), pleural effusion (5.6%), pericardial effusion (5.6%), miliary tuberculosis (5.6%), and pyrexia of unknown origin (5.6%). None of the patients with extra‐pulmonary tuberculosis had evidence of pulmonary tuberculosis. The atypical presentation with insidious onset was quite common. Anergy to tuberculin skin test was noticed in 56% of cases. All of our patients received modified antituberculosis treatment for 1 year with adequate response, and without undue side effects. We conclude that a high index of suspicion is required especially in the diagnosis of extra‐pulmonary tuberculosis, and when there is a high percentage of anergy to tuberculin skin test. Tissue biopsy both for characteristic histology and demonstration of MTB, either by staining or culture, remains the main criteria for the diagnosis of extra‐pulmonary tuberculosis.
Airborne contact dermatitis from n‐alkyl dimethylbenzylammonium chloride and n‐alkyl dimethylethyl‐benzylammonium chloride in a detergent
Authors: Mauleón Cristina , Mauleón Pablo , Chavarría Eva , De La Cueva Pablo , Suárez Ricardo , Pablo Lázaro
Published: October 2006

Occupational airborne contact dermatitis from disinfectants are not frequent. They are usually seen in hospitals, were the exposure is more common. We report a case of a young woman, with an intense eczematous eruption that developed hours after an accidental contact with a cleaning solution.
An in vitro study of the pH of three calcium hydroxide dressing materials
Authors: Zmener Osvaldo , Pameijer Cornelis H. , Banegas Gladys
Published: October 2006

Abstract –  Calcium hydroxide is widely used as a root canal dressing material because of its favorable alkalinizing effect. It has been suggested that the action comes from diffusion of hydroxyl ions through the apical foramen. The purpose of this in vitro study was to test the pH changes that occurred over a period of 30 days using a mixture of calcium hydroxide and distilled water and two commercial calcium hydroxide products in a simulated periapical environment. The materials were inserted in glass tubes closed at one end, which were placed in individual vials containing distilled water at a pH 7.4. Unfilled glass tubes were used as controls. Alkalinity changes of the medium were measured at 1 and 24 h and 15 and 30 days. The alkalinizing properties of all materials showed a rapid increase at 1 and 24 h followed by a continuous but more gradual increase from 15 to 30 days. The control tubes did not cause a change in pH of the medium, which remained at pH 7.4. At the end of the observation period, the alkalinizing properties of Calasept and Ultracal XS were significantly higher (P < 0.05) than the calcium hydroxide/distilled water paste.
Control of adipogenesis in ruminants
Authors: ROH Sang‐Gun , HISHIKAWA Daisuke , HONG Yeon‐Hee , SASAKI Shinichi
Published: October 2006

Adipose tissue is an important organ that is involved in the peripheral regulation of body homeostasis, specifically, energy intake, storage and expenditure. Since fat metabolism is of the utmost importance in ruminants, the signals and mechanisms which regulate adiposity for fattening have been studied and characterized by many different approaches. Adipogenesis in the adipose tissues of ruminants is triggered and modulated by several factors/genes, some of which (conjugated linoleic acid, tumor necrosis factor‐α and adipogenin) have been examined with respect to adipogenesis in ruminants by numerous researchers, including those in our group. The purpose of this article was to describe recent advances and insights into the molecular regulating processes of preadipocyte, adipocyte and adipose tissues in ruminants.
CHARACTERIZATION OF A DUPLEX POLYMERASE CHAIN REACTION ASSAY FOR THE DETECTION OF ENTEROTOXIGENIC STRAINS OF STAPHYLOCOCCUS AUREUS
Authors: TANG JUN‐NI , SHI XIAN‐MING , SHI CHUN‐LEI , CHEN HUAN‐CHUN
Published: October 2006

Sequence analysis demonstrated that all reported primers based on the thermonuclease (TNase) gene (nuc) used in the detection of the foodborne pathogen Staphylococcus aureus were derived from the nuclease gene, instead of the thermonuclease gene. In this study, two pairs of primers targeting the sequences of the nuc and 16S ribosomal RNA genes were designed in a duplex polymerase chain reaction (PCR) assay for the detection of S. aureus, particularly those of the enterotoxigenic strains. After optimization of the amplification conditions by uniform design, two specific products were amplified in the PCR detection system: a 223‐bp nuc fragment and a 565‐bp 16S rDNA fragment. Evaluation tests demonstrated that this duplex PCR method has high specificity for only S. aureus. The detection limit of the assay was 9.35 pg/µL using S. aureus genomic DNA. The sensitivity for direct detection of milk samples sparked with S. aureus was 104–105 cfu/mL, and the sensitivity was 1 cfu/mL as an initial concentration when an enrichment process was used. A PCR‐based detection assay for enterotoxin gene was performed in parallel with the detection of the nuc‐encoded TNase activity in several S. aureus strains, and a good correlation between TNase production and enterotoxigenicity was demonstrated in all the strains tested.
DNA SEQUENCE ANALYSIS OF rpoB GENE MUTATIONS IN RIFAMPICIN‐RESISTANT MYCOBACTERIUM TUBERCULOSIS
Authors: ZAKI MAYSAA EL‐SAYED , HASSANIN NADIA
Published: October 2006

Multidrug‐resistant tuberculosis (MDR‐TB) is an increasing health problem, which contributes to mortality from tuberculosis (TB). Rifampicin (RIF) resistance is considered a marker for MDR‐TB. Resistance to RIF results from mutation in the gene encoding the beta subunit of RNA polymerase (rpoB) of the mycobacterial tuberculosis (MTB) complex.

The aim of this study was to assess the presence of RIF‐resistant TB strains using the BACTEC 460 TB system (Becton Dickinson Microbiology System, Cockeysville, MD) and to determine the pattern of rpoB gene mutations in those strains by line probe assay in combination with DNA sequence analysis.

The study was carried out on 60 patients with pulmonary TB. Sputum samples were cultured in the BACTEC 460 system. Positive TB cultures were subjected to antimycobacterial susceptibility by BACTEC 460 and agar proportional susceptibility test. RIF‐resistant strains were further evaluated by line probe assay for the presence of rpoB mutations and DNA sequence analysis for detection of type of mutation.

All sputum samples yielded growth by both conventional and BACTEC 460 system. Of the isolated TB bacilli, 20.0, 20.7, 6.7 and 3.3% were resistant to RIF, isoniazid (INH), ethambutol and streptomycin, respectively. Twenty percent were MDR‐TB. The line probe assay had 100% sensitivity and 95.8% specificity. The most common mutations detected by DNA sequencer were detected within the 69‐bp hypervariable region of the rpoB gene, mostly His 526Tyr and Ser531 Leu mutations.

From this study, we could conclude that the most frequent drug resistance of TB was for RIF and INH. The most frequent sequence mutations were detected within the 69‐bp hypervariable region of the rpoB gene as His526Tyr and Ser531 Leu mutations. The line probe assay was a simple, reliable and rapid screening tool for early detection and characterization of RIF‐resistant Mycobacterium tuberculosis strains.
Gender and Ethnic Differences in Marital Assimilation in the Early Twentieth Century
Authors: Sassier Sharon
Published: October 2006

Historical research on intermarriage has overlooked how distinctive patterns of ethnic settlement shape partner choice and assumed that the mate selection process operated the same way for men and women. This study utilizes a sample of young married adults drawn from the 1910 Census IPUMS to examine 1) whether ethnic variation in partner choice was shaped by differences in group concentration and distribution and 2) if factors shaping outmarriage were gendered. About one fifth of young married Americans had spouses of a different ethnic background in 1910, though there was considerable ethnic variation in outmarriage propensities. Barriers to intermarriage fell at different rates, depending upon ethnic group, sex, and region of settlement; they were weakest for first- and second-generation English men. Structural factors such as group size operated differently for men and women; while larger group representation increased men's odds of outmarriage to both native stock and other white ethnic wives, women from the ethnic groups with the largest presence were significantly more likely to wed fellow ethnics than the native stock. Ultimately, even if they resided in the same location, the marriage market operated in different ways for ethnic women and men in search of mates.
Assessing the Advantages of Bilingualism for the Children of Immigrants
Authors: Golash-Boza Tanya
Published: October 2006

This article responds to the current academic debate on the advantages of bilingualism to the children of immigrants in the United States. The author utilizes data from the 1992–1993 and 1995–1996 Children of Immigrants Longitudinal Study to estimate the effects of bilingualism on educational outcomes. In contrast to a recent study, the author provides conclusive evidence that there are advantages to bilingualism beyond the functional ability to communicate with one's parents. The author also provides evidence that demonstrates that bilingualism is only advantageous in those communities with low levels of English proficiency and high levels of resources and networks.
Between Ideology and Pragmatism: The Politics of Dual Nationality in Germany
Authors: Green Simon
Published: October 2006

This article discusses the policy and politics of dual nationality in Germany. It contrasts the policy reality, in which dual nationality is tolerated in a wide range of cases, with Germany's continued opposition in principle to this phenomenon. It then analyzes political, cultural and electoral factors to explain why this opposition persists despite these widespread exceptions. In conclusion, the article argues that by continuing formally to oppose dual nationalities, Germany in effect discourages naturalizations and thereby continues to operate a broadly exclusive citizenship.
Acute Stroke Care at Rural Hospitals in Idaho: Challenges in Expediting Stroke Care
Authors: Gebhardt James G. , Norris Thomas E.
Published: October 2006

ABSTRACT: 
Context: Thrombolytics are currently the most effective treatment for stroke. However, the National Institute for Neurological Disorders and Stroke criteria for initiation of thrombolytic therapy, most notably the 3‐hour time limit from symptom onset, have proven challenging for many rural hospitals to achieve. Purpose: To provide a snapshot of stroke care at rural hospitals in Idaho and to investigate the experiences of these hospitals in expediting stroke care. Methods: Using a standard questionnaire, a telephone survey of hospital staff at 21 rural hospitals in Idaho was performed. The survey focused on acute stroke care practices and strategies to expedite stroke care. Findings: The median number of stroke patients treated per year was 23.3. Patient delays were reported by 77.8% of hospitals, transport delays by 66.7%, in‐hospital delays by 61.1%, equipment delays by 22.2%, and ancillary services delays by 61.1%. Approximately 67% of hospitals had implemented a clinical pathway for stroke and 80.0% had provided staff with stroke‐specific training. No hospitals surveyed had a designated stroke team, and only 33.3% reported engaging in quality improvement efforts to expedite stroke care. Thrombolytics (tPA) were available and indicated for stroke at 55.6% of the hospitals surveyed. Conclusions: Rural hospitals in Idaho face many difficult challenges as they endeavor to meet the 3‐hour deadline for thrombolytic therapy, including limited resources and experience in acute stroke care, and many different types of prehospital and in‐hospital delays.
Practice Locations of Graduates of Family Physician Residency and Nurse Practitioner Programs: Considerations Within the Context of Institutional Culture and Curricular Innovation Through Titles VII and VIII
Authors: Edwards Joellen B. , Wilson Jim L. , Behringer Bruce A. , Smith Patricia L. , Ferguson Kaethe P. , Blackwelder Reid B. , Florence Joseph A. , Bennard Bruce , Tudiver Fred
Published: October 2006

ABSTRACT: 
Background: Studies have described the aggregate results of federal funding for health professions education at the national level, but analysis of the long‐term impact of institutional participation in these programs has been limited. Purpose: To describe and assess federally supported curricular innovations at East Tennessee State University designed to promote family medicine and nurse practitioner graduate interest in rural and underserved populations. Methods: Descriptive analysis of a survey to determine practice locations of nurse practitioner graduates (1992‐2002) and graduates of 3 family medicine residencies (1978‐2002). Graduates’ (N = 656) practice locations were documented using specific federal designations relating to health professions shortages and rurality. Results: Overall, 83% of family medicine residency and 80% of nurse practitioner graduates selected practice locations in areas with medically underserved or health professions shortage designations; 48% of family physicians and 38% of nurse practitioners were in rural areas. Conclusions: Graduates who study in an educational setting with a mission‐driven commitment to rural and community health and who participate in curricular activities designed to increase their experience with rural and underserved populations choose, in high numbers, to care for these populations in their professional practice.
Physical and Mental Health and Access to Care Among Nonmetropolitan Veterans Health Administration Patients Younger Than 65 Years
Authors: West Alan , Weeks William B.
Published: October 2006

ABSTRACT: 
Context: The 4.5 million military veterans treated by the Veterans Health Administration (VA) are believed to experience poorer physical and mental health than nonveterans. Furthermore, nonmetropolitan residents have less access to medical services, whether or not they are veterans in VA care. A direct comparison of metropolitan and nonmetropolitan veterans and nonveterans on a national health survey has not been reported, so it is not known whether nonmetropolitan VA patients experience similar medical need or access as other nonmetropolitan residents. Purpose: We sought to compare the perceptions of health status and access to care among metropolitan and nonmetropolitan veterans in VA care, other veterans, and nonveterans in a large national sample surveyed under the same conditions. Methods: Male respondents to the 2000 Behavioral Risk Factor Surveillance System health survey were divided into veterans or nonveterans, VA users or nonusers, metropolitan or nonmetropolitan residents, and 1 of 3 age groups (18‐44, 45‐64, and 65+). Responses to questions about current health status, health coverage, and access to care were submitted to chi‐square analyses or analyses of variance, using SUDAAN software to compute survey error variance. Findings: Nonmetropolitan VA patients younger than 65 years consistently reported the worst physical and mental health status and reduced access to care. Conclusions: VA can anticipate increasing demand for mental and physical health care among rural veterans younger than 65 years.
Tautochronic Vibration Absorbers for Rotating Systems
Authors: Shaw Steven W. , Schmitz Peter M. , Haddow Alan G.
Published: October 2006

This paper describes an analytical and experimental investigation of the dynamic response and performance of a special type of centrifugal pendulum vibration absorber used for reducing torsional vibrations in rotating systems. This absorber has the property that it behaves linearly out to large amplitudes, and thus experiences no frequency detuning. Previous analytical work on such tautochronic absorbers has considered the response, dynamic stability, and performance of single- and multi-absorber systems. In particular, it is known that these absorbers, when perfectly tuned to the order of the applied torque, do not exhibit hysteretic jumps in the response, but multi-absorber systems can experience instabilities that destroy the symmetry of their synchronous response. In this work we extend the theory to include linear de-tuning of the absorbers, which can be used as a design parameter to influence absorber performance, both in terms of rotor vibration reduction and operating range. This paper reviews the basic analysis, which employs scaling and averaging, and extends it to include the detuning. In addition, systematic experiments of systems with one and two absorbers are carried out. The experimental results are unique in that the test facility is capable of varying the excitation order, thereby allowing one to obtain order-response curves that are useful for design purposes. The experimental results are found to be in excellent agreement with the analytical predictions, and these clearly demonstrate the tradeoffs faced when selecting absorber tuning.
Characterization of in situ diffusion of silver in Ge–Te amorphous films for programmable metallization cell memory applications
Authors: Lee Soo-Jin , Yoon Soon-Gil , Choi Kyu-Jeong , Ryu Sang-Ouk , Yoon Sung-Min , Lee Nam-Yeal , Yu Byoung-Gon
Published: October 2006

Silver-rich GeTe solid electrolytes for use in programmable metallization cell (PMC) memory devices were prepared by the in situ diffusion of silver into the GeTe films during the deposition of silver by rf sputtering on GeTe chalcogenide glass films. The concentration of silver in the silver-rich GeTe films was controlled by adjusting the concentration of Te in the GeTe films. A PMC memory device with a Ag(300nm)∕Agx(Ge45Te55)1−x(200nm)∕TiW(100nm) structure and a device diameter of 0.5μm showed reproducible memory characteristics based on resistive switching at low voltage with high Roff∕Ron ratios. The PMC memory device exhibited good switching characteristics up to 100cycles at an amplitude of ±2V and a pulse width of 1μs.
Pencil beam approach for correcting the energy dependence artifact in film dosimetry for IMRT verification
Authors: Kirov Assen S. , Caravelli Gregory , Palm Åsa , Chui Chen , LoSasso Thomas
Published: October 2006

The higher sensitivity to low‐energy scattered photons of radiographic film compared to water can lead to significant dosimetric error when the beam quality varies significantly within a field. Correcting for this artifact will provide greater accuracy for intensity modulated radiation therapy (IMRT) verification dosimetry. A procedure is developed for correction of the film energy‐dependent response by creating a pencil beam kernel within our treatment planning system to model the film response specifically. Film kernels are obtained from EGSnrc Monte Carlo simulations of the dose distribution from a diameter narrow beam in a model of the film placed at six depths from in polystyrene and solid water phantoms. Kernels for different area phantoms ( and polystyrene and solid water) are produced. The Monte Carlo calculated kernel is experimentally verified with film, ion chamber and thermoluminescent dosimetry (TLD) measurements in polystyrene irradiated by a narrow beam. The kernel is then used in convolution calculations to predict the film response in open and IMRT fields. A photon beam and Kodak XV2 film in a polystyrene phantom are selected to test the method as they are often used in practice and can result in large energy‐dependent artifacts. The difference in dose distributions calculated with the film kernel and the water kernel is subtracted from film measurements to obtain a practically film artifact free IMRT dose distribution for the Kodak XV2 film. For the points with dose exceeding (11% of the peak dose) in a large modulated field and a film measurement inside a large polystyrene phantom at depth of , the correction reduces the fraction of pixels for which the film dose deviates from dose to water by more than 5% of the mean film dose from 44% to 6%.
The use of a commercial QA device for daily output check of a helical tomotherapy unit
Authors: Alaei Parham , Hui Susanta K. , Higgins Patrick D. , Gerbi Bruce J.
Published: October 2006

Helical tomotherapy radiation therapy units, due to their particular design and differences from a traditional linear accelerator, require different procedures by which to perform routine quality assurance (QA). One of the principal QA tasks that should be performed daily on any radiation therapy equipment is the output constancy check. The daily output check on a Hi‐Art TomoTherapy unit is commonly performed utilizing ionization chambers placed inside a solid water phantom. This provides a good check of output at one point, but does not give any information on either energy or symmetry of the beam, unless more than one point is measured. This also has the added disadvantage that it has to be done by the physics staff. To address these issues, and to simplify the process, such that it can be performed by radiation therapists, we investigated the use of a commercially available daily QA device to perform this task. The use of this device simplifies the task of daily output constancy checks and eliminates the need for continued physics involvement. This device can also be used to monitor the constancy of beam energy and cone profile and can potentially be used to detect gross errors in the couch movement or laser alignment.
Experimental determination of the effect of detector size on profile measurements in narrow photon beams
Authors: Pappas E. , Maris T. G. , Papadakis A. , Zacharopoulou F. , Damilakis J. , Papanikolaou N. , Gourtsoyiannis N.
Published: October 2006

The aim of this work is to investigate experimentally the detector size effect on narrow beam profile measurements. Polymer gel and magnetic resonance imaging dosimetry was used for this purpose. Profile measurements of a diameter stereotactic beam were performed using polymer gels. Eight measurements of the profile of this narrow beam were performed using correspondingly eight different detector sizes. This was achieved using high spatial resolution two‐dimensional measurements and eight different signal integration volumes slice thickness, simulating detectors of different size. “” ranged from 0.25 to , representing the detector size. The gel‐derived profiles exhibited increased penumbra width with increasing detector size, for sizes . By extrapolating the gel‐derived profiles to zero detector size, the true profile (Pt) of the studied beam was derived. The same polymer gel data were also used to simulate a small‐volume ion chamber profile measurement of the same beam, in terms of volume averaging. The comparison between these results and actual corresponding small‐volume chamber profile measurements performed in this study, reveal that the penumbra broadening caused by both volume averaging and electron transport alterations (present in actual ion chamber profile measurements) is a lot more intense than that resulted by volume averaging effects alone (present in gel‐derived profiles simulating ion chamber profile measurements). Therefore, not only the detector size, but also its composition and tissue equivalency is proved to be an important factor for correct narrow beam profile measurements. Additionally, the convolution kernels related to each detector size and to the air ion chamber were calculated using the corresponding profile measurements , the gel‐derived true profile (Pt), and convolution theory. The response kernels of any desired detector can be derived, allowing the elimination of the errors associated with narrow beam profile measurements.
In vivo and phantom measurements of the secondary photon and neutron doses for prostate patients undergoing IMRT
Authors: Reft Chester S. , Runkel‐Muller Renate , Myrianthopoulos Leon
Published: October 2006

For intensity modulated radiation therapy (IMRT) treatments photons are typically used, however, for deep seated tumors in the pelvic region, higher photon energies are increasingly being employed. IMRT treatments require more monitor units (MU) to deliver the same dose as conformal treatments, causing increased secondary radiation to tissues outside the treated area from leakage and scatter, as well as a possible increase in the neutron dose from photon interactions in the machine head. Here we provide in vivo patient and phantom measurements of the secondary out‐of‐field photon radiation and the neutron dose equivalent for IMRT treatments. The patients were treated for prostate cancer with IMRT at institutions using different therapy machines and treatment planning systems. Phantom exposures at the different facilities were used to compare the secondary photon and neutron dose equivalent between typical IMRT delivered treatment plans with a six field three‐dimensional conformal radiotherapy (3DCRT) plan. For the in vivo measurements thermoluminescent detectors (TLDs) and detectors using optically stimulated radiation were used to obtain the photon dose and CR‐39 track etch detectors were used to obtain the neutron dose equivalent. For the phantom measurements a Bonner sphere ( diameter) containing two types of TLDs (TLD‐600 and TLD‐700) having different thermal neutron sensitivities were used to obtain the out‐of‐field neutron dose equivalent. Our results showed that for patients treated with IMRT the photon dose equivalent is greater than the neutron dose equivalent measured outside the treatment field and the neutron dose equivalent normalized to the prescription dose varied from 2 to among the therapy machines. The Bonner sphere results showed that the ratio of neutron equivalent doses for the IMRT and 3DCRT prostate treatments scaled as the ratio of delivered MUs. We also observed differences in the measured neutron dose equivalent among the three therapy machines for both the in vivo and phantom exposures.
Towards a theory of a solution space for the biplane imaging geometry problem
Authors: Singh Vikas , Xu Jinhui , Hoffmann Kenneth R. , Xu Guang , Chen Zhenming , Gopal Anant
Published: October 2006

Biplane angiographic imaging is a primary method for visual and quantitative assessment of the vasculature. In order to reliably reconstruct the three‐dimensional (3D) position, orientation, and shape of the vessel structure, a key problem is to determine the rotation matrix and the translation vector which relate the two coordinate systems. This so‐called Imaging Geometry Determination problem is well studied in the medical imaging and computer vision communities and a number of interesting approaches have been reported. Each such technique determines a solution which yields 3D vasculature reconstructions with errors comparable to other techniques. From the literature, we see that different techniques with different optimization strategies yield reconstructions with equivalent errors. We have investigated this behavior, and it appears that the error in the input data leads to this equivalence effectively yielding what we call the solution space of feasible geometries, i.e., geometries which could be solutions given the error or uncertainty in the input image data. In this paper, we lay the theoretical framework for this concept of a solution space of feasible geometries using simple schematic constructions, deriving the underlying mathematical relationships, presenting implementation details, and discussing implications and applications of the proposed idea. Because the solution space of feasible geometries encompasses equivalent solutions given the input error, the solution space approach can be used to evaluate the precision of calculated geometries or 3D data based on known or estimated uncertainties in the input image data. We also use the solution space approach to calculate an imaging geometry, i.e., a solution.
Optimization of three‐dimensional angiographic data obtained by self‐calibration of multiview imaging
Authors: Noël Peter B. , Hoffmann Kenneth R. , Kasodekar Snehal , Walczak Alan M. , Schafer Sebastian
Published: October 2006

Stroke is one of the leading causes of death in the U.S. The treatment of stroke often involves vascular interventions in which devices are guided to the intervention site often through tortuous vessels based on two‐dimensional (2‐D) angiographic images. Three dimensional (3‐D) vascular information may facilitate these procedures. Methods have been proposed for the self‐calibrating determination of 3‐D vessel trees from biplane and multiple plane images and the geometric relationships between the views (imaging geometries). For the biplane analysis, four or more corresponding points must be identified in the biplane images. For the multiple view technique, multiple vessels must be indicated and only the translation vectors relating the geometries are calculated. We have developed methods for the calculation of the 3‐D vessel data and the full transformations relating the multiple views (rotations and translations) obtained during interventional procedures, and the technique does not require indication of corresponding points, but only the indication of a single vessel, e.g., the vessel of interest. Multiple projection views of vessel trees are obtained and transferred to the analysis computer. The vessel or vessels of interest are indicated by the user. Using the initial imaging geometry determined from the gantry information, 3‐D vessel centerlines are calculated using the indicated centerlines in pairs of images. The imaging geometries are then iteratively adjusted and 3‐D centerlines recalculated until the root‐mean‐square (rms) difference between the calculated 3‐D centerlines is minimized. Simulations indicate that the 3‐D centerlines can be accurately determined (to within ) even for errors in indication of the vessel endpoints as large as . In phantom studies, the average rms difference between the pairwise calculated 3‐D centerlines is approximately prior to refinement (i.e., using the gantry information alone), whereas the average rms difference is usually below after refinement. Accuracies and reliabilities of better than were also determined by comparing centerlines determined using multiview and rotational angiography reconstruction and clinical data sets. These results indicate that the multiview approach will provide accurate and reliable 3‐D centerlines for indicated vessel(s) without increasing the dose to the patient.
A ranklet‐based image representation for mass classification in digital mammograms
Authors: Masotti Matteo
Published: October 2006

Regions of interest (ROIs) found on breast radiographic images are classified as either tumoral mass or normal tissue by means of a support vector machine classifier. Classification features are the coefficients resulting from the specific image representation used to encode each ROI. Pixel and wavelet image representations have already been discussed in one of our previous works. To investigate the possibility of improving classification performances, a novel nonparametric, orientation‐selective, and multiresolution image representation is developed and evaluated, namely a ranklet image representation. A dataset consisting of 1000 ROIs representing biopsy‐proven tumoral masses (either benign or malignant) and 5000 ROIs representing normal breast tissue is used. ROIs are extracted from the digital database for screening mammography collected by the University of South Florida. Classification performances are evaluated using the area under the receiver operating characteristic curve. By achieving values of and 90% sensitivity with a false positive fraction value of 4.5%, experiments demonstrate classification results higher than those reached by the previous image representations. In particular, the improvement on the value over that achieved by the wavelet image representation is statistically relevant with the two‐tailed value . Besides, owing to the tolerance that the ranklet image representation reveals to variations in the ROIs’ gray‐level intensity histogram, this approach discloses to be robust also when tested on radiographic images having gray‐level intensity histogram remarkably different from that used for training.
Modeling Single-Neuron Dynamics and Computations: A Balance of Detail and Abstraction
Authors: Herz Andreas V. M. , Gollisch Tim , Machens Christian K. , Jaeger Dieter
Published: October 2006

The fundamental building block of every nervous system is the single neuron. Understanding how these exquisitely structured elements operate is an integral part of the quest to solve the mysteries of the brain. Quantitative mathematical models have proved to be an indispensable tool in pursuing this goal. We review recent advances and examine how single-cell models on five levels of complexity, from black-box approaches to detailed compartmental simulations, address key questions about neural dynamics and signal processing.
High-Performance Photorefractive Polymers
Authors: Liphardt Martin , Goonesekera Arosha , Jones Brian E. , Ducharme Stephen , Takacs James M. , Zhang Lei
Published: October 2006

Photorefractive materials can form "instant" holograms without time-consuming development steps. Their potential applications include image processing, optical data storage, and correction of image distortion, but the cost of crystal growth and preparation has been a primary impediment to commercial application. Polymers, on the other hand, are low in cost and readily fabricated in a variety of forms. Photorefractive polymers were constructed with performance that matched or exceeded the performance of available photorefractive crystals. The largest observed two-beam energy coupling gain coefficient for the polymers was 56 per centimeter.
In Vivo Ca
2+
Dynamics in a Cricket Auditory Neuron: An Example of Chemical Computation
Authors: Sobel Erik C. , Tank David W.
Published: October 2006

Fura-2 calcium imaging in the cricket omega neuron revealed increased intracellular free calcium ion concentration in response to simulated cricket calling songs and other sound stimuli. The time course of the increase and decrease in intracellular calcium coincided with the time course of forward masking, a time-dependent modulation of auditory sensitivity. The buffering of calcium transients with high concentrations of a kinetically fast calcium buffer eliminated the post-stimulus hyperpolarization associated with forward masking, whereas the uncaging of calcium inside the neuron produced a hyperpolarization. The results suggest that sound-stimulated intracellular calcium accumulation acts by means of a calcium-activated hyperpolarizing current to produce forward masking. These findings underscore the importance of chemical dynamics in neural computation by demonstrating a behaviorally relevant role of calcium dynamics in vivo.
Synthesis, Isolation, and Equilibration of 1,9- and 7,8-C
70
H
2
Authors: Henderson Craig C. , Rohifing Celeste McMichael , Gillen Kenneth T. , Cahill Paul A.
Published: October 2006

Equilibration of 1,9- and 7,8-C
70
H
2
has allowed the relative free energy of these isomers to be measured. These "simplest hydrocarbon derivatives of C
70
" are formed by hydroboration of C
70
at room temperature. Analysis of the platinum-catalyzed equilibration of these isomers yielded a relative free energy at 295 kelvin of 1.4 ± 0.2 kilocalories per mole, with the 1,9 isomer being more stable. This value is in excellent agreement with the ab initio HF/6-31 G
*
calculated energy difference of 1.3 kilocalories per mole, whereas semiempirical calculations gave poor agreement.
Controlling Molecular Order in "Hairy-Rod" Langmuir-Blodgett Films: A Polarization-Modulation Microscopy Study
Authors: Gupta V. K. , Kornfield J. A. , Ferencz A. , Wegner G.
Published: October 2006

The interplay of molecular weight, layer thickness, and thermal annealing in controlling molecular order in ultrathin Langmuir-Blodgett films is characterized with the use of polarization-modulation laser-scanning microscopy. The degree and direction of molecular alignment can be imaged rapidly and sensitively through the magnitude and orientation of linear dichroism in Langmuir-Blodgett films of rodlike poly(phthalocyaninatosiloxane) (PcPS). Images are presented for films as thin as two molecular layers (∼44 angstroms). Molecular alignment along the transfer direction is much stronger for films of PcPS with ∼25 repeat units (∼10 nanometers long) than for those with ∼50 repeat units (∼20 nanometers long). Enhancement of alignment by thermal annealing is also much greater for PcPS-25 than PcPS-50. Intimate interaction with the substrate suppresses improvement in alignment by annealing, evident by an anomalously small increase in anisotropic absorption of the first two layers.