Simultaneous equations in ordered discrete responses with regressor-dependent thresholds

Summary The parameters of ordered discrete response (ODR) models are identified only up to a positive scale. In this paper, we examine the identification issue for simultaneous equations with ODR, where the well-known identification problem in simultaneous equations of recovering structural-form parameters from reduced-form parameters is compounded with the ODR identification problem. We allow the thresholds in ODR to be regressor dependent as well as constant; the former is particularly challenging because threshold parameters get mixed with regression parameters, adding one more dimension to the identification problem. We also explore a cross-equation restriction on threshold differences, under which the structural form parameters are fully identified as if the dependent variables are continuously distributed. An empirical example with farm–household joint labour supply is provided to illustrate the identification issues, to show how our proposals work and to apply tests devised for the threshold constancy and cross-equation restrictions.     

Outcomes with bilateral cochlear implantation following sudden dual sensory loss after ethylene glycol poisoning

Abstract

Acute loss of vision accompanied by profound loss of hearing is fortunately rare, but has a catastrophic effect on both the patient and their family. Re-establishing communication and spatial awareness are high priorities. We describe the case of a 45 year-old man who presented as a result of poisoning by ethylene glycol. Following assessment by clinicians who learned the deaf-blind alphabet in order to communicate, he had his hearing successfully rehabilitated with simultaneous bilateral cochlear implants. The patient recovered the ability to understand speech near perfectly in quiet, to attend to the ear giving the clearer signal in noise, and to localise sources of sound. The patient reported that the latter skill facilitated mobility. This is the first reported case of a patient with acute dual sensory loss due to ethylene glycol poisoning benefiting from bilateral cochlear implants.     

Débordement de masquage normal et anormal sur les aigus

Upward Spread of Masking in Normal and Impaired Ears

Upward spread of masking was studied for normals and sensorineurally hearing-impaired subjects with high-frequency hearing loss. Hearing-impaired listeners were recruited in such a way as to present normal hearing on the frequency of the masker, that is a narrow band of noise centered at 1 000 Hz. Levels of the masker were set at 70, 80 and 90 dB, respectively. Results first indicated the presence of a relationship between masked and elevated absolute thresholds for a masker level of 70 dB. At masker levels of 80 and 90 dB, hearing-impaired listeners showed excessive upward spread of masking in spite of normal hearing sensitivity at the masker frequency: with 80 and 90 dB of noise, upward spread of masking grew, respectively, 2.6 and 1.6 times faster than in normals. Furthermore, excessive upward spread of masking was shown to progress as a function of hearing loss. Results were interpreted as additional evidence of abnormal frequency selectivity in sensorineurally hearing-impaired listeners.     

Treatment strategy for colorectal cancer with resectable synchronous liver metastases:Is any evidence-based strategy possible?

Fifteen percent to twenty-five percent of patients affected by colorectal cancer presents with liver metastases at diagnosis. In resectable cases, surgery is the only potentially curative treatment and achieves survival rates up to 50% at 5 years. Management is complex, as colorectal resection, liver resection, chemotherapy, and, in locally advanced mid/low rectal tumors, radiotherapy have to be integrated. Modern medical practice usually relies on evidence-based protocols. Levels of evidence for synchronous metastases are poor:published studies include few recent prospective series and several retrospective analyses collecting a limited number of patients across long periods of time. Data are difficult to be generalized and are mainly representative of single centre’s experience, biased by local recruitment, indications and surgical technique. In this context, surgeons have to renounce to "evidence-based medicine" and to adopt a sort of "experience-based medicine". Anyway, some suggestions are possible. Simultaneous colorectal and liver resection can be safely performed whenever minor hepatectomies are planned, while a case-by-case evaluation is mandatory in case of more complex procedures. Neoadjuvant chemotherapy is preferentially scheduled for patients with advanced metastatic tumors to assess disease biology and to control lesions. It can be safely performed with primarytumor in situ , even planning simultaneous resection at its end. Locally advanced mid/low rectal tumor represents a further indication to neoadjuvant therapies, even if treatment’s schedule is not yet standardized. In summary, several issues have to be solved, but every single HPB centre should define its proper strategy to optimize patient’s selection, disease control and safety and completeness of surgery.     

局部晚期非小细胞肺癌放疗剂量提升研究进展

局部晚期非小细胞肺癌的RTOG0617研究显示进一步提高放疗剂量并没有带来生存获益,这促进了剂量提升策略的改变。目前多项研究通¹⁸FDG高摄取区域局部加量、同步加量调强放疗、改变剂量分割模式等探索更为有效的剂量提升手段,并取得一系列进展。PET-CT技术及调强放疗技术的广泛应用,为放疗剂量优化和提升提供了广阔空间。     

Modeling Methods for Mixture-of-Mixtures Experiments Applied to a Tablet Formulation Problem

During the past few years, statistical methods for the experimental design, modeling, and optimization of mixture experiments have been widely applied to drug formulation problems. Different methods are required for mixture-of-mixtures (MoM) experiments in which a formulation is a mixture of two or more “major” components, each of which is a mixture of one or more “minor” components. Two types of MoM experiments are briefly described. A tablet formulation optimization example from a 1997 article in this journal is used to illustrate one type of MoM experiment and corresponding empirical modeling methods. Literature references that discuss other methods for MoM experiments are also provided.     

Acute myocardial infarction due to simultaneous spasm of 3 coronary arteries that worsened over time

Coronary artery spasm (CAS) rarely worsens from single-vessel to simultaneous multivessel CAS naturally, and simultaneous multivessel CAS leads to serious conditions such as cardiopulmonary arrest (CPA). A 77-year-old Japanese man who took medications for CAS was transferred to our hospital due to persistent chest pain. On arrival, his vital signs were stable, but his electrocardiogram (ECG) showed ST-segment elevation in leads II, III and aVF. Ventricular fibrillation developed suddenly. Although routine cardiopulmonary resuscitation (CPR) including intravenous administration of epinephrine was performed immediately, he could not be resuscitated. After initiation of percutaneous cardiopulmonary support (PCPS), there was a return of spontaneous circulation. His ECG showed exacerbation of myocardial ischemia with ST-segment elevation in leads I, II, III, aVL, aVF and V3–V6. Emergency coronary angiography revealed severe CAS of the right and left coronary arteries, which was relieved completely by intracoronary administration of nitrates. He was diagnosed with acute myocardial infarction due to simultaneous 3-vessel CAS that progressed over time. About 6 h after arrival, he developed hemodynamic instability and died. CAS worsened from single-vessel to simultaneous 3-vessel spasm, and intracoronary administration of nitrates was effective in relieving CAS, which was documented by the ECG and coronary angiogram. Since CAS can progress over time, nitrates must be administered immediately. When CAS leads to CPA, epinephrine may be ineffective in CPR because of its vasoconstrictive effect on coronary arteries; therefore, PCPS should be initiated, and intracoronary nitrates should be administered.     

Dosimetry and techniques for simultaneous hyperthermia and external beam radiation therapy

An increased biological effect is realized when hyperthermia and radiation therapy are combined simultaneously. To take advantage of this effect, techniques have been developed that combine existing hyperthermia devices with a linear accelerator. This allows concomitant delivery of either ultrasound or microwave hyperthermia with photon radiation therapy. Two techniques have been used clinically: the orthogonal technique, in which the microwave or ultrasound beam and the radiation beam are orthogonal to one another, and the en face technique, in which the ultrasound or microwave beam and the radiation beam travel into the tumour through the same treatment window. The en face technique has necessitated the development of special attachments so that the hyperthermia device can be mounted to the linear accelerator and so that non-uniform portions of the hyperthermia device can be removed from the radiation beam. For microwave therapy, applicators are mounted onto the linear accelerator using the compensating filter tray holder. For ultrasound, special reflector devices are mounted to a frame that is mounted onto the compensating filter tray holder of the linear accelerator. Because the linear accelerator is an isocentric device, the height of the radiation source is fixed, and this has necessitated specially designed devices so that the ultrasound support system is compatible with the linear accelerator. The treatment setups for both the en face technique and the orthogonal technique require the interaction of both hyperthermia and radiation therapy personnel and equipment. The dosimetry and day-to-day operations for each technique are unique. The simulation for the en face technique is much different from the simulation of a normal radiation treatment and requires the presence of a hyperthermia physicist. Also, for the en face technique, the attenuation of the microwave applicator and the thickness and attenuation of the ultrasound reflector system are taken into account for radiation dosimetry. This paper presents details of the dosimetry and logistics of the techniques for simultaneous thermoradiotherapy based on 7 years of experience treating more than 50 patients.     

HPLC同时测定慢性阻塞性肺病患者血浆中的茶碱和1,3-二甲基尿酸

目的 采用HPLC法同时测定慢性阻塞性肺病(COPD)患者血浆中的茶碱及其代谢物1,3-二甲基尿酸(1,3-DMU).方法 色谱柱为Hypersil BDS C18柱(250 mm×4.6 mm,5μm),流动相为乙腈-水(7∶93),流速1 mL·min-1,检测波长280 nm.43名COPD患者连续服用茶碱(100 mg,bid)两周后,测定茶碱及1,3-DMU的血药浓度.结果 茶碱、1,3-DMU的线性范围分别为0.20 ～ 10.00 μg∶ mL-1(r=0.9998)、0.05 ～ 2.00 μg∶ mL-(r=0.9996);日内、日间RSD均≤12.91％,提取回收率分别为77.52％ ～79.22％、71.69％ ～ 74.02％;患者的平均茶碱血药浓度为3.57±1.59 μg∶ mL-1,茶碱和1,3-DMU的浓度呈强相关(r=0.672),1,3-DMU/茶碱为0.064±0.024.结论 所用方法简便、快速、准确,可用于COPD患者茶碱血药浓度的监测,1,3-DMU与茶碱浓度的比值可评估不同个体对茶碱清除率的差异.