Fractal patterns in the parameter space of a bistable Duffing oscillator.

We study the dissipative bistable Duffing oscillator with equal energy wells and observe fractal patterns in the parameter space of driving frequency, forcing amplitude, and damping ratio. Our numerical investigation reveals the Hausdorff fractal dimension of the boundaries that separate the oscillator's intrawell and interwell behaviors. Furthermore, we categorize the interwell behaviors as three steady-state types: switching, reverting, and vacillating. While fractal patterns in the phase space are well known and heavily studied, our results point to another research direction about fractal patterns in the parameter space. Another implication of this study is that the vibration of a continuous bistable system modeled using a single-mode approximation also manifests fractal patterns in the parameter space. In addition, our findings can guide the design of next-generation bistable and multistable mechanical metamaterials.

pH Dependence of Liquid-Liquid Phase Separation in Organic Aerosol.

Atmospheric aerosol particles influence climate through their direct and indirect effects. These impacts depend in part on the morphology of the particles, which is determined by their composition. The effect of pH on morphology was investigated using particles composed of 3-methylglutaric acid and ammonium sulfate by manipulating the starting pH of the bulk solution through the addition of aqueous sodium hydroxide. Efflorescence, deliquescence, phase separation, and mixing transitions were observed with optical microscopy. Due to changes in its protonation states, the solubility of the organic component increases with increasing pH, which shifts the location of the separation relative humidity (SRH) from 78.7% for the fully protonated acid to 63.9% for the fully deprotonated acid. Surprisingly, this shift in the SRH leads to hysteresis between the SRH and the mixing relative humidity (MRH). Particle pH has the greatest effect on phase transitions that require nucleus formation, that is, efflorescence and SRH.

Management of Painful Recurrent Intermetatarsal Neuroma Using Processed Porcine Extracellular Matrix Material: A Case Report.

Painful recurrent stump neuroma presents a common clinical problem following the transection of a nerve after initial interdigital neuroma excision but there is no gold standard of treatment. A patient presented with pain symptoms consistent with recurrent intermetatarsal stump neuroma after undergoing previous surgery to excise a Hauser neuroma. The recurrent stump neuroma was excised and the resulting nerve was capped and implantation into intrinsic muscle. Postoperatively, the patient experienced a complete resolution of pain and return of normal function. This article discusses capping material characteristics and considers the factors that may contribute to clinical success.

Impact of alleles at the Yellow Burley (Yb) loci and nitrogen fertilization rate on nitrogen utilization efficiency and tobacco-specific nitrosamine (TSNA) formation in air-cured tobacco.

Tobacco-specific nitrosamine (TSNA) formation in tobacco is influenced by alkaloid levels and the availability of nitrosating agents. Tobacco types differ in their potential for TSNA accumulation due to genetic, agronomic, and curing factors. Highest TSNA concentrations are typically measured in burley tobaccos. One of the main genetic differences between burley and all other tobacco types is that this tobacco type is homozygous for recessive mutant alleles at the Yellow Burley 1 (Yb(1)) and Yellow Burley 2 (Yb(2)) loci. In addition, burley tobacco is typically fertilized at higher nitrogen (N) rates than most other tobacco types. This study utilized nearly isogenic lines (NILs) differing for the presence of dominant or recessive alleles at the Yb(1) and Yb(2) loci to investigate the potential influence of genes at these loci on TSNA accumulation. Three pairs of NILs were evaluated at three different nitrogen fertilization rates for alkaloid levels, nitrogen physiology measures, and TSNA accumulation after air-curing. As previously observed by others, positive correlations were observed between N application rates and TSNA accumulation. Recessive alleles at Yb(1) and Yb(2) were associated with increased alkaloid levels, reduced nitrogen use efficiency, reduced nitrogen utilization efficiency, and increased leaf nitrate nitrogen (NO(3)-N). Acting together, these factors contributed to significantly greater TSNA levels in genotypes possessing the recessive alleles at these two loci relative to those carrying the dominant alleles. The chlorophyll-deficient phenotype conferred by the recessive yb(1) and yb(2) alleles probably contributes in a substantial way to increase available NO(3)-N during curing and, consequently, increased potential for TSNA formation.

Dorsal foot pain due to compression of the deep peroneal nerve by exostosis of the metatarsocuneiform joint.

Podiatric physicians often encounter patients with dorsal foot pain related to either an exostosis or a ganglion arising at the junction of the first metatarsal and the cuneiform. Removal of the exostosis or ganglion is routine but may not relieve the pain. Exostosis surgery can result in worsening of pain owing to injury of the deep peroneal nerve. In this retrospective series, ten patients with dorsal foot pain-related exostosis or ganglion underwent measurement of the cutaneous pressure threshold of the skin of the dorsal first web space to determine whether compression of the deep peroneal nerve was related to their symptoms. The Pressure-Specified Sensory Device (Sensory Management Services LLC, Baltimore, Maryland) was used for this measurement bilaterally, and the results were compared with age-related normative data. Ninety percent of the patients had abnormal sensibility in the first dorsal web space. During surgery, each patient was noted to have a site of compression of the deep peroneal nerve by the extensor hallucis brevis tendon at the metatarsocuneiform exostosis. Patients with compression of the deep peroneal nerve had pain relief in the immediate postoperative period and have remained pain-free for a mean of 14 months (range, 1-22 months). Neurosensory testing can identify pain related to the deep peroneal nerve in patients with a dorsal exostosis or ganglion in this region.

Effect of pelvic lymph node irradiation in salvage therapy for patients with prostate cancer with a biochemical relapse following radical prostatectomy.

Radiation therapy (RT) as salvage treatment for a biochemical relapse following prostatectomy has been shown to be of benefit measured by serum prostate-specific antigen (PSA) control. However, identifying a target volume for RT has not been well established in this setting. In this study, the results of postoperative RT delivered to extended fields (EFs), prostatic fossa, and pelvic lymph nodes encompassing at least the obturator lymph nodes are compared with treatment of limited fields (LFs), prostatic fossa only, as salvage treatment for patients with a biochemical relapse. Between 1987 and 1999, 68 patients were referred for postprostatectomy RT. Of these patients, 46 were treated for salvage intent by RT alone without adjuvant hormones, 21 patients were treated to EFs and 25 treated to LFs. All patients were treated using 4-field plans. The mean field sizes measured 15 x 14 cm (AP/PA fields) and 12 x 14 cm LFs for the EFs and 10 x 10 cm (AP/PA fields) and 10 x 10 cm (lateral fields) for the LFs. The mean total doses for the EFs and LFs were 6300 and 6200 cGy, respectively, using 180-cGy daily increments. All patients treated to the EFs received boost doses to the prostatic fossa after 4500 cGy total dose to the pelvis. The 10-year actuarial biochemical disease-free survival (DFS) rates for the EF and LF groups were 52% and 47%, respectively (P = 0.523). The distant metastasis-free survival (DMFS) rates were 77% and 78% (P = 0.925), and overall survival (OS) rates were 88% and 68% (P = 0.615) for the EF and LF group, respectively. A subset analysis of patients with adverse pathologic features (including tumor-involved surgical margins, lymph node involvement, seminal vesicle involvement, extracapsular extension, and/or perineural invasion) showed biochemical DFS rates of 57% and 44% (P = 0.217) for the EF and LF groups, respectively. The DMFS rates were 84% and 72% (P = 0.423), and OS rates 92% and 61% (P = 0.366) for the EF and LF groups, respectively. For patients with increasing PSA levels after a radical prostatectomy, salvage irradiation is a viable option for biochemical control. Our results suggest that EF radiation with coverage of pelvic lymph nodes shows a trend toward better PSA control in those with adverse pathologic features, although statistical significance was not achieved because of the limited number of patients who satisfied the restricted criteria excluding use of adjuvant hormones.

Diagnosis, clinical staging, and treatment of breast cancer: a retrospective multiyear study of a large controlled population.

This study compares diagnosis, staging, and treatment of newly diagnosed breast cancer cases over a several-year period. The study design was a retrospective, multiyear comparison between new breast cancer cases diagnosed in 1995 (n = 827) and 1997 (n = 815). Cases were identified through claims data, and medical record abstraction was used to verify each case and to identify clinical staging and type of treatment. All medical records were reviewed by one physician to maximize internal reliability. Both cohorts were predominantly 40 and older, white, married, and postmenopausal. The latter cohort (1997) had a higher proportion of women aged 70 to 79 and a lower proportion of women aged 40 to 49. In both cohorts, women age 40 and older were likely to be diagnosed with breast cancer at the time of mammographic screening, while women younger than 40 were more likely to be diagnosed by clinical breast examination. In logistic regression analyses, controlling for confounding factors such as age, undergoing mammographic screening increased the likelihood of having a low cancer stage at diagnosis by more than three and a half times. Mammographic screening was statistically significantly positively associated with having eligibility for breast-conserving treatment (BCT); however, although an increase in BCT eligibility was observed, actual use of BCT did not change. Mammography leads to a lower clinical stage as well as a greater likelihood of BCT eligibility at time of breast cancer diagnosis, but may not have a substantial effect on treatment choice (lumpectomy vs. mastectomy). Between 1995 and 1997, a trend was observed toward downstaging of disease at diagnosis; further research is warranted to observe whether this trend continues over time.

Postoperative radiotherapy for carcinoma of the prostate: impact on both local control and distant disease-free survival.

The role of postoperative irradiation in patients with clinically localized prostate cancer, either as an adjuvant or salvage radiotherapy, remains controversial. In this study, we evaluate the impact of postoperative radiotherapy on patients diagnosed with prostate cancer with respect to biochemical and clinical disease free survival. Between 1987 and 1996, 179 patients with clinically localized prostate cancer were found to have adverse histopathologic findings on radical prostatectomy specimens (positive surgical margins, extracapsular extension, and seminal vesicle invasion). Of these patients, 42 were referred for postoperative adjuvant radiotherapy, whereas 73 were referred for salvage irradiation because of rising serum prostate-specific antigen (PSA) levels postoperatively. The remaining 64 patients underwent prostatectomy only. The 10-year biochemical relapse-free survival (RFS) from date of surgery were 88%, 45%, and 25% for patients treated with postoperative adjuvant radiotherapy, salvage irradiation, and with surgery alone, respectively (p = 0.046). Ten-year distant RFS from date of surgery were 82%, 74%, and 44% for adjuvantly treated patients, those with salvage radiotherapy, and those with surgery alone, respectively (p = 0.0180). Ten-year overall disease RFS from date of surgery was 89%, 76%, and 30% for adjuvantly treated patients, those with salvage radiotherapy, and those with surgery alone, respectively (p = 0.0237). Multivariate analyses revealed that a preoperative PSA greater than 20 ng/ml and pathologic Gleason Score of 8 to 10 were adverse predictors for biochemical relapse, whereas pathologic Gleason Score of 8 to 10, seminal vesicle invasion, and extracapsular extension were adverse predictors of distant metastases. Postoperative radiotherapy, either delivered as adjuvant treatment for adverse histopathologic findings or as salvage therapy for local relapses, appear to confer superior local, distant disease RFS, and overall disease RFS than surgery alone.

Mammographic Screening Downstages Breast Carcinomas at Time of Diagnosis: A Community-Based Experience.

To determine the effectiveness of screening mammography in a community medical setting, data from a population-based, retrospective study was analyzed. Medical records of 827 patients with newly diagnosed breast cancer in California between October 1994 and March 1996 were reviewed. The primary care physician's record was abstracted for clinical history, including recommendation of screening mammography. The facility records where final diagnosis was made were abstracted for stage and treatment data. Among the patients who did not have previous screening mammography, 65.7% were diagnosed with "advanced" breast cancer (stages II, III, IV), while only 39.9% who had previous screening mammography were diagnosed with advanced breast cancer (p < 0.001). This study has reaffirmed that screening mammography of adult females generates downstaging at the time of diagnosis of breast cancer. Despite possession of a health insurance program and receiving educational materials, only 65% of patients over 50 years of age had screening mammography. As opposed to the once-a-year mailing of general reminders to all women 40 years old and older, developing a longitudinal electronic medical record in the managed care setting will support a more coordinated and individualized intervention based on age, date of last mammogram, and relative risk, among other factors. Continuing education efforts must also be directed to referring physicians, who may not yet recognize the value of screening mammography.