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Biomedical subjects

Hongbin Chen

Publications and source records attributed to Hongbin Chen.

10 recordsLinked to original sources
PubMed2005

Deterministic directed transport of inertial particles in a flashing ratchet potential.

Deterministic directed transport of inertia particles in a periodically on-off ratchet potential is investigated. We find that the directed transport can be induced by a finite inertia; i.e., in the overdamped case, no directed motion of the system can be observed. It is shown that a critical threshold of the ratchet asymmetry is required for the system to achieve a net current. Directed transport can be greatly enhanced when the coupling strength of particles is increased. An appropriate match of the coupling, the flashing period, and the damping can give rise to the best efficiency of transport. The commensurate effect on the directed transport, which originates from the spatial competition between the period of the potential and the static length of the coupling, is analyzed.

Journal Article↗
PubMed2005

Temporal masking in electric hearing.

Temporal masking can be defined as the detection threshold of a brief signal as a function of the signal delay in a relatively long masker. The temporal masking pattern in normal acoustic hearing reveals temporal edge enhancement in which the signal detection threshold is greater near the masker onset than in the steady-state portion. Both peripheral and central mechanisms appear to underlie temporal edge enhancement, but their relative contributions remain elusive. Cochlear implants bypass cochlear mechanical processing and stimulate the auditory nerve directly, thereby providing a unique opportunity to separate the peripheral mechanisms from the central mechanisms. Here, we systematically measured temporal masking in electric hearing by examining whether a brief signal was harder to detect at the onset than in the steady-state portion of a long masker (the "overshoot" effect). The signal and the masker were presented (1) either to the same electrode or to different electrodes, (2) at the same stimulation or different rates, and (3) in a simultaneous or an interleaved fashion. A consistent pattern of results was observed, depending on the stimulus configuration between the signal and the masker. Simultaneous stimulation at the same rate and with the same electrode produced no difference in sensitivity between the onset and the steady-state conditions, but interleaved stimulation at different rates or with different electrodes produced a significant difference. Unlike acoustic hearing, high masker levels produced an overshoot effect, and low masker levels produced an undershoot effect. Although the present results are consistent with the "on-frequency vs. off-frequency" hypothesis for the overshoot effect, results also suggest a central "same vs. different" mechanism underlying temporal masking. These results have practical implications for improving cochlear implant design.

Acoustic Stimulation↗
PubMed2005

Pilot testing of the computerized cognitive test Microcog in chemotherapy-treated older cancer patients.

BACKGROUND: Chemotherapy has a potential for inducing cognitive side effects. However, no study has focused on elderly cancer patients, a group that might be at risk for this complication. Computerized cognitive tests are available and could simplify cooperative group studies on the matter, but have not been applied to older cancer patients. METHODS: We tested the performance of Microcog (short form) in a sample of 10 consecutive cancer patients, aged 70 and older, having received chemotherapy. Patients were also asked by questionnaire to express their comments on the test. RESULTS: Six patients had never used a computer. All reported at least minor visual impairment. All did complete the test without pause. Nine out of 10 thought that most patients like them would have no problems completing the test. As a group, our patient sample generally performed within normal limits for age and education. There were a wide range of scores for the majority of the subscales, with the greatest variability of scores in Spatial Processing and Information Processing Accuracy and the least variability in reaction time. The results were robust when assessed by level of computer literacy, minor auditory and visual problems, and fluent English as a second language. CONCLUSIONS: A computer test such as Microcog appears well feasible in older cancer patients. It appears robust to comorbidity. This bodes well for a potential use of such tests in trials conducted in this patient population.

Aged↗
PubMed2005

Pitch discrimination of patterned electric stimulation.

One reason for the poor pitch performance in current cochlear-implant users may be the highly synchronized neural firing in electric hearing that lacks stochastic properties of neural firing in normal acoustic hearing. This study used three different electric stimulation patterns, jittered, probabilistic, and auditory-model-generated pulses, to mimic some aspects of the normal neural firing pattern in acoustic hearing. Pitch discrimination was measured at standard frequencies of 100, 250, 500, and 1000 Hz on three Nucleus-24 cochlear-implant users. To test the utility of the autocorrelation pitch perception model in electric hearing, one, two, and four electrodes were stimulated independently with the same patterned electric stimulation. Results showed no improvement in performance with any experimental pattern compared to the fixed-rate control. Pitch discrimination was actually worsened with the jittered pattern at low frequencies (125 and 250 Hz) than that of the control, suggesting that externally introduced stochastic properties do not improve pitch perception in electric stimulation. The multiple-electrode stimulation did not improve performance but did not degrade performance either. The present results suggest that both "the right time and the right place" may be needed to restore normal pitch perception in cochlear-implant users.

Aged↗
PubMed2004

A comprehensive geriatric intervention detects multiple problems in older breast cancer patients.

UNLABELLED: Studies of comprehensive geriatric assessment (CGA) have shown the importance of follow-up for effectiveness, but this has not been tested in an oncology clinic. In this pilot study, we enrolled 15 early breast cancer patients, aged 70 and older. They received a multidisciplinary CGA every 3 months and structured follow-up from the SAOP nurse practitioner, dietitian, social worker, and pharmacist according to risk. Total follow-up was 6 months. Median age of evaluable patients was 79 years (range 72-87). Median number of comorbidities by Cumulative Index Rating Scale-Geriatric (CIRS-G) was 5 (3-9) at baseline. Ten patients were at pharmacological risk, five at psychosocial risk, and eight at nutritional risk. Patients presented on average six problems initially, and three new problems during follow-up. The intervention directly influenced oncological treatment in four cases. It ensured continuity/coordination of care in seven cases. Success rate in addressing problems was 87%. Mean Functional Assessment of Cancer Treatment-Breast (FACT-B) scores improved from 110.5 (S.D. 16.7) to 116.3 (S.D. 16.5) (t=0.025). Function and independence were maintained. CONCLUSIONS: Older patients with early breast cancer have a high prevalence of comorbidity. A CGA with follow-up has potential for improving the treatment and prognosis of these patients and is feasible in an academic oncology setting.

Aged↗
PubMed2004

Frequency modulation detection in cochlear implant subjects.

Frequency modulation (FM) detection was investigated in acoustic and electric hearing to characterize cochlear-implant subjects' ability to detect dynamic frequency changes and to assess the relative contributions of temporal and spectral cues to frequency processing. Difference limens were measured for frequency upward sweeps, downward sweeps, and sinusoidal FM as a function of standard frequency and modulation rate. In electric hearing, factors including electrode position and stimulation level were also studied. Electric hearing data showed that the difference limen increased monotonically as a function of standard frequency regardless of the modulation type, the modulation rate, the electrode position, and the stimulation level. In contrast, acoustic hearing data showed that the difference limen was nearly a constant as a function of standard frequency. This difference was interpreted to mean that temporal cues are used only at low standard frequencies and at low modulation rates. At higher standard frequencies and modulation rates, the reliance on the place cue is increased, accounting for the better performance in acoustic hearing than for electric hearing with single-electrode stimulation. The present data suggest a speech processing strategy that encodes slow frequency changes using lower stimulation rates than those typically employed by contemporary cochlear-implant speech processors.

Adult↗
PubMed2003

Are older French patients as willing as older American patients to undertake chemotherapy?

PURPOSE: A view often held in Europe is that older Europeans are less willing than older Americans to undertake chemotherapy. This study assesses whether this view is valid. PATIENTS AND METHODS: Three-hundred twenty outpatients aged 70 years and older were interviewed via anonymous questionnaires: French patients with and without cancer and American patients with and without cancer. The response rate was 61% (195 of 320 questionnaires). Ages ranged from 70 to 95 years (29% aged 80 years and older). Two scenarios were presented: a strong chemotherapy (platinum/taxane combination-like) and a milder chemotherapy (weekly vinorelbine-like). The options were to refuse chemotherapy or to accept for a threshold chance of cure, of life prolongation, or of symptom relief. Functional status, education, self-rated health, and depression were controlled for. RESULTS: French noncancer patients (34%) were less willing to accept the strong chemotherapy than French cancer patients (77.8%), American noncancer patients (73.8%), and American cancer patients (70.5%) (P <.001 for each pair). This was also true for the moderate chemotherapy (67.9% v 100%, 95.2%, and 88.5%, respectively; P <.001). Age and sex did not correlate with response, but self-rated health, cancer status, and nationality did. Thresholds varied from patient to patient. CONCLUSION: Whereas older French people without cancer are more reluctant than older Americans to envision chemotherapy, older cancer patients in both countries have the same amenability to treatment. Chemotherapy options should be fully discussed with older cancer patients, given that most are willing to consider them.

Aged↗
PubMed2003

Can older cancer patients tolerate chemotherapy? A prospective pilot study.

BACKGROUND: To the authors' knowledge, few data currently are available regarding the tolerance to chemotherapy in older cancer patients. This prospective pilot study evaluated the changes in functional, mental, nutritional, and comorbid status, as well as the quality of life (QOL), in geriatric oncology patients receiving chemotherapy. METHODS: Sixty patients age > or = 70 years who were undergoing cancer chemotherapy were recruited in a university-based comprehensive cancer center. Changes in physical function were measured by the Eastern Cooperative Oncology Group performance status (ECOG PS) and Instrumental Activities of Daily Living (IADLs), mental health changes were measured by the Mini-Mental State Examination and the Geriatric Depression Scale (GDS), comorbidity was measured by Charlson's index and the Cumulative Illness Rating Scale-Geriatric, nutrition was measured by the Mini-Nutritional Assessment, and QOL was measured by the Functional Assessment of Cancer Therapy-General (FACT-G). Changes were assessed at baseline and at the end of treatment (EOT). Grade 4 hematologic and Grade 3-4 nonhematologic toxicities were recorded. RESULTS: Thirty-seven patients (63%) completed both assessments. Older cancer patients demonstrated a significant decline in measurements of physical function after receiving chemotherapy, as indicated by changes in scores on the IADL (P = 0.04) and on the physical (P = 0.01) and functional (P = 0.03) subscales of the FACT-G. They also displayed worse scores on the GDS administered postchemotherapy (P < 0.01). Patients who experienced severe chemotoxicity had more significant declines in ECOG PS (P = 0.03), IADL (P = 0.03), and GDS (P = 0.04), and more gain in the social well-being subscale (P = 0.02) of the FACT-G, than those who did not experience severe chemotoxicity. However, changes in most scores were small in magnitude clinically. No significant change was found between baseline and EOT in nutrition, comorbidity, and other aspects of the FACT-G. CONCLUSIONS: Older cancer patients undergoing chemotherapy may experience toxicity but generally can tolerate it with limited impact on independence, comorbidity, and QOL levels. It is important to recognize and monitor these changes during geriatric oncology treatment.

Activities of Daily Living↗
PubMed2003

Decisions for hospice care in patients with advanced cancer.

OBJECTIVES: To identify factors that may influence the decision of whether to enter a hospice program or to continue with a traditional hospital approach in patients with advanced cancer and to understand their decision-making process. DESIGN: Cross-sectional structured interview. SETTING: One community-based hospice and three university-based teaching hospitals. PARTICIPANTS: Two hundred thirty-four adult patients diagnosed with advanced lung, breast, prostate, or colon cancer with a life expectancy of less than 1 year: 173 hospice patients and 61 nonhospice patients receiving traditional hospital care. MEASUREMENTS: Hospice and nonhospice patients' demographic, clinical, and other patient-related characteristics were compared. Multivariate analysis was then conducted to identify variables associated with the hospice care decision in a logistic regression model. Information sources regarding hospice care and people involved in the hospice decision were identified. RESULTS: Patients receiving hospice care were significantly older (average age 69 vs 65 years, P =.009) and less educated (average 11.9 vs 12.9 years, P =.031) and had more people in their households (average 1.66 vs 1.16 persons, P =.019). Hospice patients had more comorbid conditions (1.30 vs 0.93, P =.035) and worse activities of daily living scores (7.01 vs 6.23, P =.030) than nonhospice patients. Hospice patients were more realistic about their disease course than their nonhospice counterparts. Patients' understanding of their prognoses affected their perceptions of the course of their disease. Hospice patients preferred quality of life to length of life. In the multivariate analysis, lower education level and greater number of people in the household were associated with the decision to enter hospice. A healthcare provider first told most of those who entered hospice about hospice. Families largely made the final decision to enter hospice (42%), followed by patients themselves (28%) and physicians (27%). CONCLUSION: The decision to enter hospice is related to demographic, clinical, and other patient-related characteristics. This study suggests that the decision-making process for hospice care in patients with advanced cancer is multidimensional. The healthcare community may better meet the end-of-life care needs of advanced cancer patients through enhanced communication with patients and families, including providing accurate prognoses and better understanding of patients' preferences and values.

Adult↗