Quantitative Predictions of Moisture-Driven Photoemission Dynamics in Metal Halide Perovskites via Machine Learning

Metal halide perovskite (MHP) photovoltaics may become a viable alternative to standard Si-based technologies, but the current lack of long-term stability precludes their commercial adoption. Exposure to standard operational stressors (light, temperature, bias, oxygen, and water) often instigate optical and electronic dynamics, calling for a systematic investigation into MHP photophysical processes and the development of quantitative models for their prediction. We resolve the moisture-driven light emission dynamics for both methylammonium lead tribromide and triiodide thin films as a function of relative humidity (rH). With the humidity and photoluminescence time series, we train recurrent neural networks and establish their ability to quantitatively predict the path of future light emission with 18% error over 4 h. Together, our in situ rH-PL measurements and machine learning forecasting models provide a framework for the rational design of future stable perovskite devices and, thus, a faster transition toward commercial applications.

Machine Learning Roadmap for Perovskite Photovoltaics

Perovskite solar cells (PSC) are a favorable candidate for next-generation solar systems with efficiencies comparable to Si photovoltaics, but their long-term stability must be proven prior to commercialization. However, traditional trial-and-error approaches to PSC screening, development, and stability testing are slow and labor-intensive. In this Perspective, we present a survey of how machine learning (ML) and autonomous experimentation provide additional toolkits to gain physical understanding while accelerating practical device advancement. We propose a roadmap for applying ML to PSC research at all stages of design (compositional selection, perovskite material synthesis and testing, and full device evaluation). We also provide an overview of relevant concepts and baseline models that apply ML to diverse materials problems, demonstrating its broad relevance while highlighting promising research directions and associated challenges. Finally, we discuss our outlook for an integrated pipeline that encompasses all design stages and presents a path to commercialization.

Humidity-Induced Photoluminescence Hysteresis in Variable Cs/Br Ratio Hybrid Perovskites

Hybrid organic-inorganic perovskites containing Cs are a promising new material for light-absorbing and light-emitting optoelectronics. However, the impact of environmental conditions on their optical properties is not fully understood. Here, we elucidate and quantify the influence of distinct humidity levels on the charge carrier recombination in Cs _xFA_{1- x}Pb(I _yBr_{1- y})₃ perovskites. Using in situ environmental photoluminescence (PL), we temporally and spectrally resolve light emission within a loop of critical relative humidity (rH) levels. Our measurements show that exposure up to 35% rH increases the PL emission for all Cs (10-17%) and Br (17-38%) concentrations investigated here. Spectrally, samples with larger Br concentrations exhibit PL redshift at higher humidity levels, revealing water-driven halide segregation. The compositions considered present hysteresis in their PL intensity upon returning to a low-moisture environment due to partially reversible hydration of the perovskites. Our findings demonstrate that the Cs/Br ratio strongly influences both the spectral stability and extent of light emission hysteresis. We expect our method to become standard when testing the stability of emerging perovskites, including lead-free options, and to be combined with other parameters known for affecting material degradation, e.g., oxygen and temperature.

Leptin and adiponectin receptor expression in oesophageal cancer

BACKGROUND

Oesophageal adenocarcinoma is an exemplar model of an obesity-associated adenocarcinoma. Altered secretion of adipokines by visceral fat is believed to play a key role in tumorigenesis. This study examined leptin receptor (ObR) and adiponectin receptor (AdipoR1 and AdipoR2) expression in oesophageal cancer, and its relationship with patient obesity status, clinicopathological data and patient survival.

METHODS

Tissue microarrays were constructed from paraffin-embedded oesophagectomy specimens. ObR, AdipoR1 and AdipoR2 expression was quantified by immunohistochemistry. Anthropometric data were measured at the time of diagnosis, and obesity status was assessed using visceral fat area determined by computed tomography and body mass index. Receptor expression was correlated with various clinicopathological and anthropometric variables. Patient survival was estimated using the Kaplan-Meier method, and results compared between those with low versus high receptor expression. A Cox multivariable regression model was used to assess the relationship between survival and a number of co-variables.

RESULTS

All 125 tumours analysed expressed AdipoR1 and AdipoR2, whereas 96·8 per cent expressed ObR. There was no significant difference in tumour pathological features or patient obesity status between tumours with low versus high ObR expression. A high level of AdipoR1 expression was significantly associated with increased patient age, obesity and less advanced tumour (T) category. Expression of AdipoR2 was inversely associated with T category (P = 0.043). Low AdipoR1 expression was an independent predictor of improved overall survival (hazard ratio 0.56, 95 per cent confidence interval 0.35 to 0.90; P = 0.017).

CONCLUSION

The association between adiponectin receptor expression, obesity status and tumour category and survival suggests a potential mechanism linking obesity and oesophageal cancer.

Changes in plasma amino acids during conditioning therapy prior to bone marrow transplantation: Their relevance to antioxidant status

Bone marrow transplant (BMT) recipients undergo a bimodal regimen of conditioning therapy, the precise prescription being dependent upon the primary disease of the individual patient. Generally, this treatment consists of chemotherapy and total body irradiation prior to transplantation, although the latter may or may not be included in the regimen. We have investigated amino acid metabolism and oxidant status in in a small series of BMT recipients before and after conditioning therapy.Plasma amino acids were measured by HPLC on 10 BMT recipients prior to commencing conditioning therapy, and again one week later before transplantation. In addition some general nutritional parameters and antioxidant components were measured. A marked decrease in the plasma concentration of a number of amino acids, especially those concerned with antioxidants, was observed over the 7 days of conditioning therapy.There is also a significant reduction in antioxidant capability, as reflected by measurements of glutathione and erythrocyte glutathione peroxidase (GSHPx), which may have an influence upon post-transplant recovery and graft function. Such a reduction in antioxidant concentrations may also have an influence upon the erythrocyte and platelet support required post-grafting.The data presented in this paper adds to the evidence for the conditional essentiality of some amino acids such as taurine and glutamine, and may support the case for specific antioxidant intervention treatment prior to, and/or after conditioning therapy together with monitoring antioxidant status during the post-grafting period.

Metabolic syndrome and leptin are associated with adverse pathological features in male colorectal cancer patients

AIM

Metabolic syndrome (MetS) describes a clustering of factors including central obesity, hypertension and raised plasma glucose, triglycerides and high-density lipoprotein (HDL) cholesterol. Central obesity is associated with a risk for colorectal cancer, but the impact of MetS on colorectal cancer biology and outcomes is unclear.

METHOD

A prospective observational study of colorectal cancer patients was carried out in an Irish population. Patients underwent metabolic and anthropometric assessment before treatment, including measurement of serum hormones and adipokines and CT measurement of visceral fat. MetS was defined according to the International Diabetes Federation definition(3) .

RESULTS

One-hundred and thirty consecutive colorectal cancer patients (66 men and 64 women) were recruited. MetS was diagnosed in 38% patients compared with the population norms reported at 21%(21) . Male patients had a significantly greater visceral fat area compared with female patients. MetS was associated with node-positive disease (P = 0.026), percentage nodal involvement (P = 0.033) and extramural vascular invasion (P = 0.049) in male patients but no significant association was observed in female patients. HDL cholesterol was also significantly associated with a more advanced pathological stage (P = 0.014) and node-positive disease (P = 0.028). Leptin was associated with nodal status (P = 0.036), microvascular invasion (P = 0.054), advanced pathological stage (P = 0.046) and more advanced Dukes stage (P = 0.042).

CONCLUSION

We report a high prevalence of MetS and visceral obesity in a colorectal cancer population. MetS and plasma leptin are associated with a more aggressive tumour phenotype in male patients only.

Pro-inflammatory and tumour proliferative properties of excess visceral adipose tissue

Obesity has been associated with increased incidence and mortality of oesophageal and colorectal adenocarcinoma. Excess central adiposity may drive this association through an altered inflammatory milieu. Utilising a unique adipose tissue bioresource we aimed to determine the pro-tumour properties of visceral adipose tissue. Comparing subcutaneous and visceral adipose tissue depots, we observed significantly higher levels of VEGF and IL-6, along with significantly higher proportions of CD8(+) T cells and NKT cells in visceral adipose tissue. Significantly higher levels of VEGF were observed in the conditioned media from visceral adipose tissue of centrally obese compared to non-obese patients. We also report a significant increase in oesophageal and colorectal tumour cell proliferation following culture with conditioned media from visceral adipose tissue of centrally obese patients. Neutralising VEGF in the conditioned media significantly decreased tumour cell proliferation. This novel report highlights a potential mechanism whereby visceral adipose tissue from centrally obese cancer patients may drive tumour progression.

T lymphocyte activation in visceral adipose tissue of patients with oesophageal adenocarcinoma

Background

Visceral adipose tissue may fuel obesity-associated chronic inflammation and tumorigenesis. T cells may be important in visceral adipose tissue in driving inflammation, but they have not yet been characterized in patients with cancer. This study aimed to characterize T lymphocytes in visceral adipose tissue and peripheral blood from patients with oesophageal adenocarcinoma.

Methods

Omental fat was taken from 35 patients with oesophageal adenocarcinoma at the start of surgery. Flow cytometry was performed to assess T cell activation status and cytokine production in omentum and peripheral blood.

Results

A large population of lymphocytes was present in the omentum. Omental CD4+ and CD8+ T cells displayed significantly enhanced expression of the T cell activation markers CD69 (P < 0·001) and CD107a (CD8+ T cells: P < 0·01), and significantly decreased CD62L expression (P < 0·05), compared with blood. Significantly higher proportions of CD45RO+ T cells compared with CD45RA+ T cells were present in omentum (P < 0·001 and P = 0·012 for CD4+ and CD8+ cells respectively). Interferon γ was the most abundant cytokine expressed by omental T cells, with a significantly higher level than in blood and subcutaneous adipose tissue (P < 0·01).

Conclusion

Visceral adipose tissue is a rich source of activated proinflammatory CD4+ and CD8+ T cells. It may fuel chronic inflammation via T cell-mediated pathways.

Leptin and gastro-intestinal malignancies

Obesity is a well-established risk factor for the development and mortality from several cancers, including adenocarcinoma of the oesophagus, oesophago-gastric junction and colorectum. Despite a large body of epidemiological evidence describing this relationship, the mechanisms relating obesity and cancer are only starting to be uncovered. The altered secretion of metabolically active, pro-inflammatory adipocytokines from adipose tissue is believed to play a key role, and leptin is believed to be a key player in obesity-related carcinogenesis, as well as being the most extensively studied of the adipokines. In this literature review, we aim to examine the association between leptin and cancers of the gastro-intestinal tract. For each individual cancer, we examine and present the published data examining the role of leptin in both cell and animal models, the association between circulating leptin levels and cancer risk, and finally the expression of the leptin system in human gastro-intestinal tract tumours, in relation to tumour biology, stage and patient outcome.

Associations between leptin and adiponectin receptor upregulation, visceral obesity and tumour stage in oesophageal and junctional adenocarcinoma

BACKGROUND

Obesity is associated with oesophageal adenocarcinoma, but mechanisms linking fat and carcinogenesis remain poorly understood. Altered circulating adipocytokines may be important. This study aimed to identify pathways through which visceral fat impacts on tumour biology.

METHODS

Seventy-five patients with oesophageal adenocarcinoma underwent anthropometric and radiological assessment of obesity. Expression of leptin receptor (ObR) and adiponectin receptors 1 and 2 (AdipR1, AdipR2) was quantified by real-time reverse transcriptase-polymerase chain reaction. The human oesophageal adenocarcinoma cell line OE33 was used as the calibrator sample.

RESULTS

Ninety-one per cent of tumours expressed ObR, 95 per cent expressed AdipR1 and 100 per cent expressed AdipR2. Relative expression of ObR was upregulated in 67 per cent, and AdipR1 and AdipR2 were downregulated in 55 and 68 per cent respectively, relative to the calibrator sample. Upregulated ObR and AdipR2 expression was significantly associated with anthropometric and radiological measures of obesity. Upregulated ObR was associated with advanced tumour and node category (P = 0.036 and P = 0.025 respectively), and upregulated AdipR2 with nodal involvement (P = 0.037).

CONCLUSION

Obesity is associated with upregulated ObR and AdipR2 expression in oesophageal adenocarcinoma. The association of ObR and AdipR2 with tumour stage suggest that pathways involving adipocytokines affect tumour biology.

Outcomes in achalasia from a surgical unit where pneumatic dilatation is first-line therapy

The management of achalasia remains controversial, with little consensus on the optimal patient treatment pathway. In our own esophageal unit, we offer pneumatic dilatation as the initial therapy in most patients as first-line therapy. In this study, we aimed to examine the safety and efficacy of our own approach to the management of patients with a diagnosis of achalasia, examining symptomatic outcomes, patient satisfaction, and need for further intervention, as well as examining patient factors associated with treatment failure. Sixty-seven consecutive patients underwent pneumatic dilatation as first-line therapy (53% male, mean age 46 years). All attended regular outpatient follow-up (mean 37, range 3-132 months). Twenty-five percent of patients required a second intervention because of symptom recurrence, at a median period of 4.5 months. Symptomatic outcomes were excellent or good in 80%. Significant predictors of treatment failure and poor symptom score included a younger age at the time of diagnosis and increased esophageal diameter on barium swallow. This study suggests that pneumatic dilatation is a safe and effective approach as first-line therapy in patients with newly diagnosed achalasia.

'Keep at it! Accept the challenges of your critics'. An interview with John M. Howard, MD, professor Emeritus, Division of General Surgery, University of Toledo, Toledo, Ohio, USA. Interview by Martín E. Fernández-Zapico

In this article, Professor John Howard shares with our readers his life experiences as a pancreatic surgeon-researcher and gives advice to junior pancreatologists starting a career in pancreatic research. Professor Howard made an outstanding contribution to the understanding of acute pacreatitis and he is a pioneer in the development of management approaches for pancreatic diseases.

Percutaneous cholecystostomy--a safe option in the management of acute biliary sepsis in the elderly

Percutaneous cholecystostomy (PC) has been used in the management of acute cholecystitis and biliary sepsis in patients with severe comorbidities where emergency cholecystectomy or open cholecystostomy are considered to carry prohibitive risks of mortality. We reviewed three consecutive cases of elderly patients with biliary sepsis presenting acutely to our unit who were managed successfully with this approach, and present herein these cases and a review of the literature.

Conservative management resulting in complete resolution of a double intussusception in an adult haemophiliac

Acute abdominal pain in haemophiliacs should be approached as haemorrhage until proven otherwise. With advancements in factor repletion and coagulopathic management a conservative approach should be considered. We describe a case of double colo-colonic intussusception lead by an intramural haematoma occurring spontaneously and resolving with conservative management in a young haemophiliac. This demonstrates that intussusception in these cases may be transient, and does not require surgical intervention.

Conception rates and serum progesterone concentration in dairy cattle administered gonadotropin releasing hormone 5 days after artificial insemination

The objectives of this study were to determine the effect of administration of exogenous GnRH 5days after artificial insemination (AI) on ovarian structures, serum progesterone concentration, and conception rates in lactating dairy cows. In experiment 1, 23 Holstein cows were synchronized using the Ovsynch protocol. Five days after AI (day 0) cows were assigned randomly to receive either saline (saline; n=11) or 100microg GnRH (GnRH; n=12). To examine ovarian structures, ultrasonography was performed on day 1 and every other day beginning on day 5 until day 13. On days 5 and 13 blood samples were obtained to measure serum progesterone concentrations. All cows in the GnRH-treated group developed an accessory corpus luteum (CL), whereas cows in the saline group did not. Mean serum progesterone concentrations did not differ between GnRH and saline groups on day 5 (1.64+/-0.46ng/ml versus 2.04+/-0.48ng/ml). On day 13 serum progesterone concentrations were greater (P<0.05) in the GnRH group compared with saline (5.22+/-0.46ng/ml versus 3.36+/-0.48ng/ml). In experiment 2, 542 lactating cows, at two different commercial dairies, were used to test the effect of administering GnRH 5 days after AI on conception rates. Cows were synchronized and detected for estrus according to tail chalk removal. Cows detected in estrus received AI within 1h after detection of estrus. Five days after AI, cows were assigned randomly to receive either GnRH (n=266) or saline (n=276). Pregnancy status was determined by palpation per rectum of uterine contents approximately 40 days after AI. There was no effect of farm on conception rate. There was no effect of treatment as conception rates did not differ between GnRH and saline groups (26.7% GnRH versus 24.3% saline). Regardless of treatment, days in milk, parity, milk yield, and number of services had no effect on the odds ratio of pregnancy. In summary, the results of this study indicated that GnRH administered 5 days after AI increased serum progesterone by developing an accessory CL but did not improve conception rates in dairy cattle.

The importance of human resources management in health care: a global context

BACKGROUND

This paper addresses the health care system from a global perspective and the importance of human resources management (HRM) in improving overall patient health outcomes and delivery of health care services.

METHODS

We explored the published literature and collected data through secondary sources.

RESULTS

Various key success factors emerge that clearly affect health care practices and human resources management. This paper will reveal how human resources management is essential to any health care system and how it can improve health care models. Challenges in the health care systems in Canada, the United States of America and various developing countries are examined, with suggestions for ways to overcome these problems through the proper implementation of human resources management practices. Comparing and contrasting selected countries allowed a deeper understanding of the practical and crucial role of human resources management in health care.

CONCLUSION

Proper management of human resources is critical in providing a high quality of health care. A refocus on human resources management in health care and more research are needed to develop new policies. Effective human resources management strategies are greatly needed to achieve better outcomes from and access to health care around the world.

Vascular-enteric fistulas associated with radiation therapy in patients with pancreatic adenocarcinoma

BACKGROUND

Irradiation therapy is being evaluated widely as an adjunct to therapy of resectable and unresectable pancreatic exocrine carcinoma. Exsanguinating haemorrhage has been an occasional late complication.

CASE OUTLINES

Two patients with unresectable cancer of the pancreas were treated by bypass, chemotherapy and both intra-operative and postoperative irradiation. Both patients died 5-11 months later of gastroduodenal haemorrhage from arterio-enteric fistulas, which were confirmed by autopsy but had been uncontrolled by selective embolisation. A third patient, for whom little other information was available, died of upper abdominal haemorrhage 5 months after a 'curative' resection combined with intra-operative and postoperative irradiation.

DISCUSSION

Judgement in management is difficult because of the poor prognosis from the underlying disease on the one hand versus the fact that site of bleeding has sometimes been from complicating benign disease. Better endovascular techniques of control of such haemorrhage may be developing.

Isotretinoin-induced inflammatory bowel disease in an adolescent

OBJECTIVE

To report a case of inflammatory bowel disease (IBD) associated with use of isotretinoin.

CASE SUMMARY

17-year-old boy presented with new-onset rectal bleeding after completion of a five-month course of isotretinoin. A diagnosis of ulcerative colitis was made. His condition worsened despite therapy with 5-aminosalicylic acid, steroid retention enema, iron supplement, and prednisone. Five months after the onset of rectal bleeding, he had lost 11.4 kgand developed bilateral pitting edema of the hips and profound anemia. A subtotal colectomy and ileostomy was performed.

DISCUSSION

Rectal bleeding has been reported to occur during or up to several years after treatment with isotretinoin. The mechanism by which isotretinoin may induce IBD is unknown. Proposed mechanisms include inhibition of epithelial cell growth resulting in ulceration and inflammation of the gut mucosa, inhibition of glycoprotein synthesis affecting the integrity of the mucosal wall, and stimulation of kiler T cells, leading to epithelial cell injury and a resultant inflammatory response.

CONCLUSION

This case of probable isotretinoin-induced IBD suggests that patients with suspected IBD should be asked about current or past use of isotretinoin to improve documentation of this serious adverse event.

Mechanisms of taxotere-related drug resistance in pancreatic carcinoma

BACKGROUND

Pancreatic adenocarcinoma (PAC) is generally refractory to most chemotherapeutic agents, including docetaxel (Taxotere; TXT). Specific mechanisms for TXT-related drug resistance in PAC have not been defined. The hypothesis of this study was that PAC resistance to TXT is primarily related to P-glycoprotein (P-gp), the expression product of multiple drug resistance (MDR)-1, as opposed to lung resistance protein (LRP) or multidrug resistance protein (MRP).

MATERIALS AND METHODS

The sensitivity of the PAC cell line SUIT-2 and its sublines to TXT, doxorubicin (DOX) and 5-fluorouracil (5-FU) was evaluated with a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay. MDR1 (P-gp), MRP, LRP, and beta-tubulin isotype gene expressions were detected at the messenger RNA level by reverse transcription-polymerase chain reaction (RT-PCR). Verapamil and indomethacin (IMC) were used to test the functionality of P-gp and MRP, respectively.

RESULTS

The SUIT-2 subline S-020 and the TXT-selected SUIT-2 cell line S2/TXT were significantly resistant to TXT. Both showed cross-resistance to DOX but no resistance to 5-FU. RT-PCR demonstrated strong expression of P-gp in S-020 and S2/TXT and weaker or no expression in other cells lines. MRP and LRP expression was found in most of these cell lines but had no relationship to the TXT resistance. TXT resistance in S2-020 and S2/TXT could be reversed by verapamil but not by IMC. Levels of beta-tubulin isotype II and III were increased in S2/TXT compared with S-020 and SUIT-2.

CONCLUSIONS

Intrinsic and acquired TXT resistance is primarily mediated by P-gp, but not by MRP or LRP, and is markedly reversed by the P-gp modulator verapamil. Hence future related studies should focus on the use of agents that block the transporter action of P-gp.

Optical design using computer graphics

For decades the computer has been the primary tool used for optical design. Typical tasks include performing numerical calculations for ray tracing and analysis and rendering graphics for system drawings. As machines become faster with each new generation, the time needed for a particular design task has greatly reduced, allowing multiple assignments to be performed with little noticeable delay. This lets the designer modify a system and then immediately see the results rendered in graphics with a single motion. Such visual design methods are discussed here, where graphics of systems and plots relating to their performance are produced in real time, permitting the optical designer to design by pictures. Three examples are given: an educational tutorial for designing a simple microscope objective, an unobstructed reflective telescope composed of three spherical mirrors, and a modified Offner relay with an accessible pupil.

Invasiveness and MMP expression in pancreatic carcinoma

BACKGROUND

Previous investigations have suggested that expression of matrix metalloproteinases (MMPs) may be related to increased invasiveness of various tumors. This study evaluated a possible relation between pancreatic tumor cell invasiveness and MMPs.

METHODS

A Matrigel invasion assay was performed with pancreatic tumor cell line SUIT-2 and its sublines S2-007, S2-013, S2-020, and S2-028. The degree of invasiveness of stimulated and unstimulated cell lines was correlated with MMP gene expression measured by RT-PCR and MMP protein product measured by gelatin zymography. Cell lines were stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA), concanavalin (Con-A), and polymerized collagen type I gel (Vitrogen).

RESULTS

For SUIT-2, S2-007, S2-013, S2-020, and S2-028, 3.2, 1.0, 4.1, 6.4, and 0.4%, respectively, of the cells invaded the Matrigel membrane. TPA, Con-A, and Vitrogen resulted in the up-regulation of MMP-2 in S2-020. TPA and Vitrogen resulted in up-regulation of MMP-9 in each of the cell lines, while Con-A could up-regulate MMP-9 expression only in SUIT-2. There was no constitutive expression of either MMP-2 or MMP-9 in SUIT-2 or its sublines. There was a positive relationship between Matrigel invasiveness and up-regulation of MMP-2 and MMP-9 expression.

CONCLUSION

These data suggest that, while MMP-2 and MMP-9 are not constitutively expressed in pancreatic carcinoma cell lines, they may be up-regulated by TPA, Con-A, and Vitrogen. Since MMP-2 and MMP-9 expression correlated with degree of tumor cell invasiveness, the ability to up-regulate MMP-2 and MMP-9 expression may play a role in facilitating pancreatic tumor cell invasion.

Imaging with three spherical mirrors

Unobstructed, plane-symmetric systems of three spherical mirrors are investigated. Twelve parameters are necessary to specify the configuration of such a system. Constraints are determined to eliminate four of these parameters as independent degrees of freedom. These constraints ensure appropriate first-order behavior and are used to aid in two example design studies--one for a class of systems with the object at infinity and another for a class of finite conjugate projection systems. For the first study, a portion of the associated merit-function space is systematically evaluated and plotted, and the results are compared with those obtained when a global optimizer is used. For the second study, a global optimizer is employed as the primary search tool. Example systems from both studies are presented.

Imaging with four spherical mirrors

We investigate unobstructed, plane-symmetric imaging systems of four spherical mirrors. Fifteen parameters are necessary to specify the configuration of such a system. Constraints are determined that ensure that any resultant system possesses a given set of first-order properties. These constraints remove four parameters as available degrees of freedom. To illustrate the efficacy of this design approach, we present two example studies: one for a class of systems with the object at infinity and another for finite-conjugate projection systems. For each study a global optimizer is used as the primary search tool. Example systems from these studies are presented.

Flow limitation in infants assessed by negative expiratory pressure

Forced expiratory flows by the rapid compression technique are often used to assess airway function in infants; however, it remains unclear as to whether flow limitation (FL) is achieved. Studies in adults have used negative expiratory pressure (NEP) at the airway opening as a noninvasive technique to assess whether FL is achieved. An increase in flow with NEP indicates that FL has not been achieved, whereas no increase in flow with NEP indicates FL has been achieved. In the adult studies, the change in flow was assessed by visual inspection of the flow-volume curve. We evaluated whether NEP could be used to assess FL during forced expiration in infants. In addition, we quantified the change in flow secondary to NEP. We applied -5 cm H(2)O NEP to four infants during forced expiratory maneuvers. The step increase in flow with NEP was always less than 5% at high jacket compression pressures and consistent with FL. For one subject, FL was also confirmed from isovolume pressure flow-curves measured with an esophageal catheter. We conclude that NEP can be used in infants to assess FL during forced expiratory maneuvers by the rapid compression technique.

Development and progress in resective surgery for pancreatic cancer

Pancreatoduodenectomy was developed from experience gained with transduodenal ampullectomy, preceded by a relatively bloodless cholecystoenterostomy. Although Codivilla (1898) and Kausch (1909) each achieved a single survivor following pancreatoduodenectomy, further development of the operation had to await discovery of vitamin K and a description of human blood types, the latter leading to the development of blood banks. After vitamin K and blood banks became available, Allen O. Whipple and his resident C.R. Mullins developed the two-stage pancreatoduodenectomy (1934-1935) and Whipple the one-stage procedure (1940). Although the mortality rate from pancreatoduodenectomy remained approximately 33% for more than 25 after Whipple's reports, concentration of resection in "centers of specialization" has now reduced mortality rates below 5%. Thus operative survival has been achieved, but long-term survival has not kept pace. Long-term data remain inadequate because they are usually expressed as Kaplan-Meier estimates and because of the nonuniformity of reporting (e.g., exclusion of postoperative deaths and palliative resections, intraoperative adjuvant therapies, and variations of operative techniques). Widely based Kaplan-Meier estimates of 5-year survival range from 12% to 15% after resection and more than 20% in selected categories. Total pancreatectomy has not improved short- or long-term survival rates. Extended lymphadenectomy and resection of peripancreatic soft tissues, as currently developed in several surgical clinics in Japan, suggest a higher incidence of complications but perhaps more long-term survivors. Interpretation of their data is currently subject to the same limitations noted above. As our surgical forebears needed vitamin K and blood banks to achieve postresection survival, we and our students need effective adjuvant therapy of micrometastases and better modalities for early diagnosis to improve long-term survival.

Pseudomyxoma peritonei: Sudden cardiac death complicating post operative intraperitoneal treatment with 5-fluorouracil

BACKGROUND

Pseudomyxoma peritonei, a tumor which spreads chiefly along peritoneal surfaces, has recently been treated by resection followed by intraperitoneal infusion of 5-fluorouracil (5-FU). Reports on the cardiotoxicity of this drug, given intravenously, indicate an incidence of 1.4-2.9%. Although several deaths have been reported following 5-FU therapy by continuous intravenous infusion, none has apparently been reported following bolus intravenous injection.

METHOD

Radical resection of an extensive pseudomyxoma peritonei was performed. Following convalescence, intraperitoneal infusion of 5-FU was initiated in a daily dose of 20 mg/kg body weight (1,440 mg), planned for administration in multiple 5-day cycles.

RESULTS

After three uneventful daily infusions of 5-FU, the patient suddenly died, apparently of a sudden cardiac event. Autopsy provided no explanation for his death. The coronary arteries were free of disease and no residual tumor was found. A review of the literature reveals no report of a cardiac death from 5-FU following its intraperitoneal administration.

CONCLUSIONS

The fatality suggests the potential toxicity of 5- FU when administered intraperitoneally, a factor to be considered in decisions to use this drug intraperitoneally.

Dietary intake of cobalamin in elderly people who have abnormal serum cobalamin, methylmalonic acid and homocysteine levels

OBJECTIVE

To determine if poor dietary intake can explain the cobalamin-related abnormalities often seen in the elderly.

DESIGN

Prospective laboratory survey with a follow-up dietary assessment.

SETTING

Social centers for the elderly and an outpatient clinic.

SUBJECTS

Ninety-five free-living subjects >60y old with abnormal or suspicious findings in cobalamin-related tests and 78 subjects >60y old with normal results.

INTERVENTIONS

Serum cobalamin, methylmalonic acid and homocysteine determinations to assess cobalamin status and a one year food-frequency questionnaire to assess cobalamin intake.

RESULTS

Only three of the 173 subjects (1.7%), one of whom had normal cobalamin status, ingested <2 microg cobalamin/d, the Recommended Daily Allowance. Sixty-nine subjects (39.9%) ingested <6 microg/d, but they did not have more abnormal serum cobalamin or metabolite values than those ingesting >6 microg. Ordering all subjects by quintiles according to cobalamin intake revealed no significant trends or differences in any of the serum values either. Moreover, arranging subjects by results of tests of cobalamin status showed that the subjects with abnormal cobalamin status did not differ in cobalamin intake from those with normal cobalamin status, although they did differ in use of supplements. Finally, cobalamin intake, with or without supplements, did not correlate with serum cobalamin or metabolite levels. The absence of any association between cobalamin status and intake contrasts sharply with the significant correlation between folate intake and folate status (P = 0.0001).

CONCLUSIONS

The high frequency of mildly abnormal cobalamin status in the elderly cannot be attributed to poor intake of cobalamin. Nondietary explanations, such as malabsorption and other phenomena, must always be sought to explain mild cobalamin deficiency in the elderly.

Johann Georg Wirsüng (1589-1643) and the pancreatic duct: the prosector of Padua, Italy

Although his primacy was subsequently challenged by a student, it is now known that Johann Georg Wirsüng, the prosector of Padua, Italy, discovered the human pancreatic duct in 1642 during the dissection of an executed murderer. Instead of publishing his discovery, he engraved a drawing of the duct on a copper plate, from which he made seven or more imprints. The copies were sent to leading anatomists of Europe with the question, "Should I call it an artery or a vein? I never found blood in it ...." Three and a half centuries later, the copper plate remains well preserved and the authors, to the surprise of European surgeons and librarians, but with their aid, have traced six copies of the "ductus Wirsüngianus" imprints still in existence. This is the story of Wirsüng the man, his subsequent assassination, and finally the recognition that his finding had opened a new field of science.

Carcinoid tumors of the pancreas. Status report based on two cases and review of the world's literature

CONCLUSION

The diagnosis of a pancreatic carcinoid should be based on the measurement of serotonin in serum or its demonstration in the tumor and/or by the measurement of its derivative (5-HIAA) in urine. Carcinoid of the pancreas is a rare but definite entity; usually having metastasized by the time of diagnosis. The term "serotonin-producing tumor of the pancreas" has been suggested as an alternative designation for "pancreatic carcinoid."

BACKGROUND

The literature on carcinoid tumors of the pancreas is confusing because much of it preceded the development of the more specific immunological, chemical and staining techniques currently available.

METHODS

43 case reports were collected from the world's literature, based on a demonstrable pancreatic neuroendocrine tumor plus a positive finding of at least one of the following without another dominant hormone being demonstrated: elevation of 5-Hydroxytryptamine (5-HT) (serotonin) in the serum or detected in tumor tissue, and/or elevation of 5-Hydroxyindole acetic acid (5-HIAA) in the urine. In addition to these two hormone-specific assays, information was collected on the silver-staining properties of the tumor; properties which have traditionally been associated with carcinoid tumors. Positive silver staining in tumor cells (argyrophilic and/or argentaffin reaction) is strongly indicative of the carcinoid tumor but the findings are less specific than the hormone assays and immunohistologic stains.

RESULTS

In this review of 43 cases, including two current ones, the pancreatic carcinoid tumor has the following important features: 1. It is a rare tumor that is usually diagnosed late when the tumor is large and has metastasized. Thirty-eight (88.4%) have been malignant. They are, therefore, associated with a high incidence of the "carcinoid syndrome." 2. To date, prognosis in therapy is poor, based on delayed diagnosis, a resultant low incidence of resectability, and an uncertain duration of survival after resection. 3. Pancreatic carcinoid tumors remain difficult to differentiate from other endocrine tumors. The measurement of urinary 5-HIAA excretion or the demonstration of elevated serotonin level in the tumor or in serum is essential to its distinction. Silver staining of the tumor, although of historic importance, has been superceded by the hormone-specific studies. 4. To distinguish it from other endocrine tumors of the pancreas, the terms "pancreatic serotoninoma" or "serotonin-producing tumor of the pancreas" have been suggested as possible alternatives. Its growth characteristics may be related more to its cell of origin than to its extent of hormone secretion. Not all of the tumors result in recognizable hyperserotoninemia.

Imaging a point to a line with a single spherical mirror

Methods for imaging a single point source to a line image are discussed, and a design study of single spherical mirror systems that form aberration-free line images is presented. An expression forthe ray density along the line image is derived for such systems in the cases of (i) uniform beam profiles and (ii) Gaussian beam profiles. The resulting ray density profiles are illustrated for single spherical mirror systems over a wide range of design parameters.

A comparison of omeprazole with ranitidine for ulcers associated with nonsteroidal antiinflammatory drugs. Acid Suppression Trial: Ranitidine versus Omeprazole for NSAID-associated Ulcer Treatment (ASTRONAUT) Study Group

BACKGROUND

Suppressing acid secretion is thought o reduce the risk of ulcers associated with regular use of nonsteroidal antiinflammatory drugs (NSAIDs), but the best means of accomplishing this is uncertain.

METHODS

We studied 541 patients who required continuous treatment with NSAIDs and who had ulcers or more than 10 erosions in either the stomach or duodenum. Patients were randomly assigned to double-blind treatment with omeprazole, 20 mg or 40 mg orally per day, or ranitidine, 150 mg orally twice a day, for four or eight weeks, depending on when treatment was successful (defined as the resolution of ulcer and the presence of fewer than five erosions in the stomach, and fewer than five erosions in the duodenum, and not more than mild dyspepsia). We randomly assigned 432 patients in whom treatment was successful to maintenance treatment with either 20 mg of omeprazole per day or 150 mg of ranitidine twice a day for six months.

RESULTS

At eight weeks, treatment was successful in 80 percent (140 of 174) of the patients in the group given 20 mg of omeprazole per day, 79 percent (148 of 187) of those given 40 mg of omeprazole per day, and 63 percent (110 of 174) of those given ranitidine (P<0.001 for the comparison with 20 mg of omeprazole and P=0.001 for the comparison with 40 mg of omeprazole). The rates of healing of all types of lesions were higher with omeprazole than with ranitidine. During maintenance therapy, the estimated proportion of patients in remission at the end of six months was 72 percent in the omeprazole group and 59 percent in the ranitidine group. The rates of adverse events were similar between groups during both phases. Both medications were well tolerated.

CONCLUSIONS

In patients with regular use of NSAIDs, omeprazole healed and prevented ulcers more effectively than did ranitidine.

Chylous ascites. A late complication of massive peripancreatic necrosis

A 43-yr-old female underwent a normal endoscopic retrograde cholangiopancreatography (ERCP) because of ill-defined abdominal discomfort. A life-threatening pancreatitis with massive peripancreatic necrosis ensued, necessitating multiple necrosectomies. A colonic fistula required a temporary colostomy. Thirty-three months after onset of pancreatitis, although seemingly stable, she developed a massive chylous ascites, the fluid of which had a lipid content of approx 8000 mg%. Her serum cholesterol and triglyceride levels remained normal. During her third postpancreatitis year, while under observation and without operative intervention, the ascites began to clear slowly, almost completely clearing over the ensuing 16 mo. No comparable syndrome has been detected in a literature review, although eight patients with chylous ascites, possibly associated with pancreatitis, were identified. Since the senior author, in a career in pancreatic surgery, had not previously encountered the problem and since its natural history in this patient revealed spontaneous improvement, its description seems worthwhile.

Pancreatojejunostomy: leakage is a preventable complication of the Whipple resection

BACKGROUND

Leakage of the pancreaticojejunal anastomosis has been a major complication after pancreaticoduodenectomy (Whipple operation), frequently reported in an incidence of 5 percent to 15 percent. The most widely used techniques of anastomosis have been variations of end-to-end pancreaticojejunostomy. Complicating 152 end-to-end anastomoses, done by me (including 98 for carcinoma of the pancreas or ampulla), were 5 pancreatic anastomotic leaks; the fifth patient died of this complication.

STUDY DESIGN

The death resulting from a pancreatic anastomotic fistula led me to change my technique to an end of the pancreas to side of the jejunum, mucosa-to-mucosa, pancreaticojejunostomy (intubated), a modification of the technique described by Cattell and used since 1985 by me in 56 consecutive patients. Patients were monitored for clinical evidence of a pancreatic fistula, including evaluation of amylase content in serum and, in most, in peritoneal drainage. Pancreatography through the exteriorized pancreatic catheter was possible if deemed advisable.

RESULTS

No pancreatic duct was too small or pancreas too soft to permit effective anastomosis. No clinical evidence developed of a pancreatic fistula, "sentinel bleed," or acute pancreatitis, and no patient was recognized to have a high amylase content in the peripancreatic peritoneal drainage. Results of the pancreatogram were negative in three patients with peripancreatic infections and in one with severe cholestasis.

CONCLUSIONS

Although consensus among surgeons does not exist as to technique of pancreatic anastomosis, the end-to-side, mucosa-to-mucosa pancreaticojejunostomy, intubated, has proved safer in my experience than end-to-end pancreaticojejunostomy. The experience has led me to believe that the technique may reduce the incidence of this fistula and contribute to making pancreaticojejunal leakage a preventable complication.

Hormone replacement therapy and cobalamin status in elderly women

Serum cobalamin concentrations are frequently low in the elderly but the cause is often not apparent. Because oral contraceptives have been associated with low cobalamin concentrations in young women, we compared hormone use with cobalamin status in elderly women to determine whether it could account for their unexplained low cobalamin concentrations. Thirty-eight of the 111 women had abnormal cobalamin status (defined by low cobalamin, elevated methylmalonic acid, and/or elevated homocysteine concentrations) and 73 had normal status. There was no difference in hormone use between the two groups: 7 (18.4%) of the 38 cobalamin-deficient subjects used estrogens compared with 20 (27.4%) of the 73 control subjects. No differences in hormone use were apparent either when analysis was confined to abnormal serum cobalamin concentrations alone. Similarly, the 27 women taking hormones and the 84 women not taking hormones did not have significantly different serum cobalamin or serum total homocysteine concentrations. Indeed, hormone users had slightly, though not significantly, higher cobalamin concentrations and lower homocysteine concentrations than nonusers; furthermore, hormone users also had significantly lower serum methylmalonic acid concentrations. Thus, neither cobalamin concentrations nor cobalamin metabolic status were significantly worse in elderly women taking estrogen than in those not taking it (and, if anything, may have been slightly better). Hormone use does not appear to be a significant contributor to the low cobalamin concentrations or the mild metabolic evidence of cobalamin deficiency so often seen in the elderly.

Metastatic pancreatic neuroendocrine carcinoma causing Cushing's syndrome. ACTH secretion by metastases 3 years after resection of nonfunctioning primary cancer

CONCLUSION

Following resection of a nonfunctioning neuroendocrine carcinoma of the pancreas, subsequent metastases, in the absence of a primary cancer (resected), developed the capacity to secrete ACTH and create the Cushing syndrome.

BACKGROUND

Although neuroendocrine carcinomas of the pancreas may produce one or more hormones and may switch secretion to a different hormone, no report is identified of a metastasis, in the absence of the primary tumor, developing de novo the capacity to secrete ACTH.

METHODS

A nonfunctioning islet cell carcinoma was resected and immunochemically stained for multiple hormones. Three years later hepatic metastases were partially resected and stained as before.

RESULTS

The primary cancer stained negative for ACTH and cortisol, positive for serotonin, and focally positive for gastrin. Three years later, after the development of a florid Cushing syndrome, the metastasis stained strongly for ACTH and negative for serotonin.

Pancreatitis associated with neuroendocrine (islet cell) tumors of the pancreas

BACKGROUND

The association of pancreatitis with neuroendocrine tumors of the pancreas is uncommon, whereas its association with exocrine pancreatic cancer is well recognized. Since the latter, but not the islet cell tumor, is thought to originate within the ductal system, it is not surprising that pancreatitis is less likely to result from the islet cell tumor. The senior author has recently noted that the first recognizable indication of an islet cell carcinoma may be one or more discrete attacks of acute pancreatitis.

METHODS AND RESULTS

Acute pancreatitis, resulting from an islet cell tumor, has been observed in five patients, in one of whom it had become chronic. In four of the patients, the tumor was malignant. A review of the English language literature reveals 14 such patients with pancreatitis, and 2 others have been noted in other languages (a total of 21 patients). The tumor was malignant in 15 of the 21 patients (71%). Although the development of pancreatitis was found to result from the obstruction of the duct in most patients, at least three seemed unrelated. In 12 of 21 cases (57%), an acute attack of pancreatitis, usually recurrent, was the initial syndrome, in contradistinction to pancreatitis resulting from exocrine tumors, which has usually been chronic in nature.

CONCLUSION

Pancreatitis, particularly acute pancreatitis, may result from an islet cell tumor. Although unusual, its occurrence may be the first signal of the presence of the tumor. In our experience, obstruction of the pancreatic duct by the islet cell carcinoma appears to be the important etiologic factor.