Effect of Early vs Late Inguinal Hernia Repair on Serious Adverse Event Rates in Preterm Infants: A Randomized Clinical Trial

Importance

Inguinal hernia repair in preterm infants is common and is associated with considerable morbidity. Whether the inguinal hernia should be repaired prior to or after discharge from the neonatal intensive care unit is controversial.

Objective

To evaluate the safety of early vs late surgical repair for preterm infants with an inguinal hernia.

Design, Setting, and Participants

A multicenter randomized clinical trial including preterm infants with inguinal hernia diagnosed during initial hospitalization was conducted between September 2013 and April 2021 at 39 US hospitals. Follow-up was completed on January 3, 2023.

Interventions

In the early repair strategy, infants underwent inguinal hernia repair before neonatal intensive care unit discharge. In the late repair strategy, hernia repair was planned after discharge from the neonatal intensive care unit and when the infants were older than 55 weeks' postmenstrual age.

Main Outcomes and Measures

The primary outcome was occurrence of any prespecified serious adverse event during the 10-month observation period (determined by a blinded adjudication committee). The secondary outcomes included the total number of days in the hospital during the 10-month observation period.

Results

Among the 338 randomized infants (172 in the early repair group and 166 in the late repair group), 320 underwent operative repair (86% were male; 2% were Asian, 30% were Black, 16% were Hispanic, 59% were White, and race and ethnicity were unknown in 9% and 4%, respectively; the mean gestational age at birth was 26.6 weeks [SD, 2.8 weeks]; the mean postnatal age at enrollment was 12 weeks [SD, 5 weeks]). Among 308 infants (91%) with complete data (159 in the early repair group and 149 in the late repair group), 44 (28%) in the early repair group vs 27 (18%) in the late repair group had at least 1 serious adverse event (risk difference, -7.9% [95% credible interval, -16.9% to 0%]; 97% bayesian posterior probability of benefit with late repair). The median number of days in the hospital during the 10-month observation period was 19.0 days (IQR, 9.8 to 35.0 days) in the early repair group vs 16.0 days (IQR, 7.0 to 38.0 days) in the late repair group (82% posterior probability of benefit with late repair). In the prespecified subgroup analyses, the probability that late repair reduced the number of infants with at least 1 serious adverse event was higher in infants with a gestational age younger than 28 weeks and in those with bronchopulmonary dysplasia (99% probability of benefit in each subgroup).

Conclusions and Relevance

Among preterm infants with inguinal hernia, the late repair strategy resulted in fewer infants having at least 1 serious adverse event. These findings support delaying inguinal hernia repair until after initial discharge from the neonatal intensive care unit.

Trial Registration

ClinicalTrials.gov Identifier: NCT01678638.

Necessity of routine perioperative epidural catheter placement in laparoscopic colorectal resections: a retrospective data analysis

PURPOSE

Whether epidural anesthesia leads to further improvement in the postoperative course of colorectal procedures is under discussion. The aim of this study was to evaluate the effects of minimally invasive colorectal oncological interventions without epidural anesthesia (EDA).

METHODS

This retrospective data analysis included the clinical data of all patients who underwent minimally invasive oncological colorectal resection at our clinic between January 2013 and April 2019. Of 385 patients who met the inclusion criteria, 183 (group I; 47.5% of 385) received EDA, and 202 (group II; 52.5% of 385) received transversus abdominis plane block instead. The relevant target parameters were evaluated and compared between the groups. The postoperative complications were graded according to the Clavien-Dindo classification.

RESULTS

The patients in group I (n=183; women, 77; men, 106; age 66.8 years) were younger (p=0.0035), received a urinary catheter more often (99.5% versus [vs.] 28.2% p<0.001), required longer, more frequent arterenol treatment (1.1 vs. 0.6 days; p<0.001), and had a longer intermediate care unit stay than those in group II (2.8 vs. 1.1 days; p<0.001). Postoperative pain levels were not significantly different between the groups (p=0.078). The patients in group I were able to ambulate later than those in group II (4 vs. 2 days; p<0.001). The difference in the postoperative day of the first defecation was not significant between the groups (p=0.236). The incidence of postoperative complications such as bleeding (p=0.396), anastomotic leaks (p=0.113), and wound infections (p=0.641) did not differ between the groups. The patients in group I had significantly longer hospital stays than those in group II (12.2 vs. 9.4 days; p<0.001).

CONCLUSION

EDA can be safely omitted from elective minimally invasive colorectal resections, and its omission is not accompanied by any relevant disadvantages to the patient.

Reconstruction, oversewing, or taking the anastomosis down - which surgical intervention is most potent in the treatment of anastomotic leaks following colorectal resections?

PURPOSE

Anastomotic leak (AL) following colorectal resections can be treated interventionally. However, most cases require surgical intervention. Thus, several surgical techniques are available, which intend to affect the further course positively. The aim of this retrospective analysis is to determine which surgical technique proves to have the biggest potential in reducing the morbidity and mortality as well as to minimize the need of re-interventions after AL.

METHODS

All patients with a history of AL following colorectal resection between 2008 and 2020 were analyzed. Patient's outcomes following surgical treatment of AL, including morbidity and mortality, clinical and para-clinical (laboratory examinations, ultrasound, and CT-scan) detection of AL recurrence, re-intervention rate, and the length of hospital stay were documented and correlated with the surgical technique used (e.g. simply over-sewing the AL, over-sewing the AL with the construction of a protective ileostomy, resection and reconstruction of the anastomosis, peritoneal lavage and transanal drainage, or taking the anastomosis down and constructing an end stoma).

RESULTS

A total of 2,724 colorectal resections were documented. Grade C AL occurred in 92 (4.4% AL occurrence-rate) and 31 (7.2% AL occurrence-rate) cases following colon and rectal resections, respectively. The anastomosis was not preservable in 52 and 17 cases following colon and rectal resections, respectively. Therefore, the anastomosis had been taken down and an end-stoma had been constructed. Over-sewing the AL with the construction of a protective ileostomy had the highest anastomosis preservation rate (14 of 18 cases) and lowest re-intervention rate (mean value of 1.5 re-interventions) following colon and rectal resections (7 of 9 cases; mean value, 1.5 re-interventions).

CONCLUSION

In cases where an AL is preservable, over-sewing the anastomosis and constructing a protective ileostomy has the greatest potential for positive short-term outcomes following colorectal resections.

Laparoscopic rectal resection without epidural catheters-does it work?

PURPOSE

Placement of an epidural catheter (EC) in colorectal resections is still recommended as a valid measure to achieve a low level of pain. However, EC is associated with increased invasiveness and with an increased risk of bladder emptying disorders and a decrease in blood pressure, which all relate to delayed mobilization. Preliminary data shows that EC placement may not be necessary for laparoscopic colon resections. The aim of this prospective study was to investigate how the omission of EC placement influences short-term postoperative outcomes in laparoscopic rectal resections.

METHODS

All laparoscopic rectal resections occurring between 2013 and 2020 were prospectively examined. Resections from January 2013 to February 2018 (group A) were compared with resections from March 2018 to December 2020 (group B; after the internal change of the perioperative pain regime). In addition to EC placement, the other target parameters of our study were urinary catheter placement during the inpatient stay, postoperative pain > 3 days on a numerical rating scale (NRS), mobilization in the first 5 postoperative days, time until the first postoperative bowel movement, postoperative complications according to Clavien-Dindo, intermediate care unit stay (IMC stay) in days, and hospital length of stay in days.

RESULTS

In the entire study period, 221 laparoscopic rectal resections were performed: 122 in group A and 99 resections in group B. The frequency of EC placement and urinary catheter placement, postoperative IMC stay, and hospital length of stay was significantly lower in group B (p < 0.05). The postoperative mobilization of patients in group B was possible more quickly. There were no differences in the level of pain, time until the first postoperative bowel movement, and postoperative complications according to Clavien-Dindo.

CONCLUSION

Omission of EC placement in laparoscopic rectal resections led to faster mobilization, a shorter IMC stay, and a shorter hospital stay without increasing the pain level. Postoperative complications did not change when an EC was not placed. Therefore, routine EC placement in laparoscopic rectal resections is unnecessary.

[First 18 months as certified ERAS® center for colorectal cancer : Lessons learned and results of the first 261 patients]

BACKGROUND

Enhanced recovery after surgery (ERAS®) describes a multimodal, interdisciplinary and interprofessional treatment concept that optimizes the postoperative convalescence of the patient through the use of evidence-based measures.

GOAL OF THE WORK

The aim of this article is to present the experiences of our center certified by the ERAS® Society for colorectal resections 18 months after successful implementation.

MATERIAL AND METHODS

Since the beginning of the certification 261 patients have been treated in our clinic according to the specifications of the ERAS® concept. As a comparison group the last 50 patients prior to implementation were evaluated in terms of compliance with ERAS® requirements, length of hospital stay and readmission rate, the need for care in an intensive or intermediate care ward, the number of necessary reoperations and the complication rate.

RESULTS

Compliance increased from 39.3% preERAS® to 81.1% after ERAS® implementation (p < 0.001). At the same time the length of stay of ERAS® patients was reduced from 7 days to 5 days (p = 0.001). While the rate of surgical complications was the same between the two groups (p = 0.236), nonsurgical complications occurred significantly less frequently in the ERAS® cohort (p = 0.018).

DISCUSSION

There are well-known stumbling blocks in implementing and maintaining an ERAS® concept; however, it is worthwhile for the patient to circumnavigate this and establish ERAS® as the standard treatment path.

Ptychographic characterisation of polymer compound refractive lenses manufactured by additive technology

The recent success in the development of high-precision printing techniques allows one to manufacture free-standing polymer structures of high quality. Two-photon polymerization lithography is a mask-less technique with down to 100 nm resolution that provides full geometric freedom. It has recently been applied to the nanofabrication of X-ray compound refractive lenses (CRLs). In this article we report on the characterization of two sets of CRLs of different design produced by two-photon polymerization-induced lithography.

Towards X-ray transient grating spectroscopy

The extension of transient grating spectroscopy to the x-ray regime will create numerous opportunities, ranging from the study of thermal transport in the ballistic regime to charge, spin, and energy transfer processes with atomic spatial and femtosecond temporal resolution. Studies involving complicated split-and-delay lines have not yet been successful in achieving this goal. Here we propose a novel, simple method based on the Talbot effect for converging beams, which can easily be implemented at current x-ray free electron lasers. We validate our proposal by analyzing printed interference patterns on polymethyl methacrylate and gold samples using ∼3  keV X-ray pulses.

Increasing the field of view in grating based X-ray phase contrast imaging using stitched gratings

Grating based X-ray differential phase contrast imaging (DPCI) allows for high contrast imaging of materials with similar absorption characteristics. In the last years' publications, small animals or parts of the human body like breast, hand, joints or blood vessels have been studied. Larger objects could not be investigated due to the restricted field of view limited by the available grating area. In this paper, we report on a new stitching method to increase the grating area significantly: individual gratings are merged on a carrier substrate. Whereas the grating fabrication process is based on the LIGA technology (X-ray lithography and electroplating) different cutting and joining methods have been evaluated. First imaging results using a 2×2 stitched analyzer grating in a Talbot-Lau interferometer have been generated using a conventional polychromatic X-ray source. The image quality and analysis confirm the high potential of the stitching method to increase the field of view considerably.

[Half-Dose Verteporfin Photodynamic Therapy (hdPDT) in the Treatment of Central Serous Chorioretinopathy]

BACKGROUND

To estimate the efficacy and safety profile of half-dose photodynamic therapy (hdPDT) for treating central serous chorioretinopathy (CSC).

PATIENTS AND METHODS

An interventional, retrospective case series of patients with CSC (symptoms ≧ 3 months) receiving half-dose PDT (3 mg/m2 verteporfin). The ophthalmic examination at baseline and at 8 and 16 weeks after treatment included slit-lamp biomicroscopy, indirect ophthalmoscopy, measurement of intraocular pressure (IOP), ETDRS best-corrected visual acuity (BCVA), Amsler grid screening and contrast visual acuity (CVA). Fluorescein angiography (FA), autofluorescence (FAF) and optical coherence tomography (OCT) were measured at each visit. Central macular thickness (CMT) was measured automatically.

RESULTS

12 eyes of 12 patients (10 male and 2 female patients; mean age 46.6 ± 7.91 years) were included in this study. Anatomical resolution was obtained in 10 eyes (83.4 %) at week 16, but 2 eyes (16.6 %) exhibited persistent SRD throughout the follow-up period. Baseline CMT decreased from initially 330.1 µm ± 131.3 to 205.6 µm ± 97.6 (p = 0.034) at week 8 and to 220.3 µm ± 120.1 (p = 0.05) at week 16. Visual acuity (number of total letters read) significantly improved from initially 82.8 ± 11.5 to 86.8 ± 13.9 at week 8 and 91.3 ± 13.8 at week 16 (p = 0.012). Contrast visual acuity (calculated decimal visual acuity) significantly improved from initially 0.14 ± 0.09 to 0.38 ± 0.28 (p = 0.002) at week 16. After therapy, no significant changes in RPE could be detected with FAF and no ocular adverse events were observed.

CONCLUSION

PDT with half-dose verteporfin resulted in reduced leakage in FA, enhanced visual acuity and resolution of subretinal fluid in OCT in patients with CSC, with no detected side effects of treatment.

[Can Postoperative Accelerated Lens Opacification be Limited by Lying in "Face-Down Position" after Vitrectomy with Gas as Tamponade?]

BACKGROUND

Developing a post-operative cataract after pars-plana vitrectomy (ppV) or core pars-plana vitrectomy (cppV) with gas as tamponade within 6 to 12 months is a common complication and is mostly accepted as unavoidable. Often a combined cataract-ppV surgery in the first place is recommended. The main goal of this study was to analyse the effects of a "face-down positioning" ("fdp") on the lens transparency and the phaco rate. By using the positive experience of an ergonomic body positioning it should be possible to improve the compliance during the period of "fdp" after surgery.

METHODS

During the study period of up to 24 months, we observed in a prospective, controlled, clinical and randomised pilot study 30 patients who all had undergone a ppV/cppV with sulfur hexafluoride gas tamponade (SF6 25 %). All patients of the supported group (SG) and the control group (CG) were requested to keep their face consequently downwards until the gas bubble was resorbed completely in order to avoid a direct contact with the lens. The real time in "fdp" in hours per day (24 hours) and the grade of lens opacification was documented pre- and postoperatively using a Pentacam HR (Oculus, Wetzlar).

RESULTS

The compliance of patients tested measuring the real time of "fdp" in hours per day varied largely (SG: 19.5/24; CG: 5.5/24; p < 0,0001). Cataract development was found to be directly related to the real time of "fdp". A cataract surgery was necessary mainly in the non-supported group (SG: 4/15; CG:12/15; p = 0.012). There was no lens opacification in the supported group after performing the "fdp" for at least 20 hours daily until the resorption of the gas bubble was completed. This result did not correlate with the age of the patient.

CONCLUSION

With the help of sufficient support at the disposal of the patients, it is possible to significantly improve the compliance during the period of "fdp" after surgery. In order to get a safe and painless "fdp" in bed, an ergonomic body positioning is necessary (Schaefer 2012). By practicing the "fdp" until the gas bubble is completely resorbed, the risk of developing a postoperative cataract can be reduced significantly. Provided there is a good compliance to "fdp", the gas bubble can cause the desired tamponade effect even when using shorter acting gases. By performing a consistent "fdp" it is possible to accelerate the healing process and avoid reoperations. Hereby it should even be possible to use an SF6-air mix or optionally simply air as tamponade.

[Treatment of central serous chorioretinopathy: MicroPulse photocoagulation versus bevacizumab]

PURPOSE

The aim of this study was to evaluate the treatment of central serous chorioretinopathy (CSC) with either subthreshold diode-laser MicroPulse (MP) or intravitreal bevacizumab (BCZ) using the Pro Re Nata (PRN) scheme.

METHODS

This comparative, controlled, prospective study over 10 months examined 52 eyes of 52 patients with either (a) treatment with MP at the active leakage site guided by fluorescein angiography (FA) (n=16 eyes), (b) intravitreal injection of 1.25 mg BCZ (n=10 eyes) or (c) passive observation (n=26 eyes). Outcome measures included changes in retinal pigment epithelium (RPE) leakage at FA, central macular thickness (CMT), best corrected visual acuity (BCVA) and 10° macular perimetry.

RESULTS

At the end of the study there was a 12.5 % persistent leakage in the MP group compared to 60 % in the BCZ group and 92 % in the control group. Mean CMT decreased by 94 µm in the MP, 38 µm in the BCZ and did not change in the control group. Mean BCVA improved by six ETDRS letters in the MP, decreased by one letter in the BCZ and by 2 letters in the control group. In the MP group mean perimetric deficit improved by 1.5 decibels and corrected lost variance by 2.6. In the BCZ it improved by 0.6 and by 0.5 in the control group. Retreatment was required in 7 out of 16 eyes of the SDM (43.75 %), and in 5 out of 10 eyes of the BCZ group (50 %).

CONCLUSIONS

MP photocoagulation was superior to intravitreal injections of 1.25 mg BCZ in the treatment of CSC which resulted in enhanced visual acuity and macular perimetry.

[Significant improvement in compliance with the face-down position after vitrectomy and gas tamponade]

BACKGROUND

The positioning of a patient in a "prone position" ("face down position", fdp) after pars plana vitrectomy with gas tamponade has been discussed controversially since the beginning of macular surgery. The "prone positioning" is almost standard although the duration varies. In most of the study designs for macular surgery "face-down positioning" is advised. However it is not clearly described how the "prone position" was achieved. In most of the studies it is not shown if the patients had suitable aids and how long and how efficiently they used them. Experience while practising this shows that the patient's compliance is a great challenge. Patients are mostly unable to comply, which could result in refusal.

METHODS

In our prospective, controlled and randomised pilot study we observed postoperatively 40 patients who all underwent a pars-plana vitrectomy and sulfur hexafluoride-gastamponade (SF6 25%). All patients of the supported group (SG) and the control group (CG) were requested to keep their face downwards until the gas bubble was resorbed completely. In the postoperative time in hospital the participants of the SG used a simple prone-positioning support. In the time at home after hospital, the patients were supplied with an inflatable device. In this trial we wanted to show whether or not it is possible to improve the patient's compliance by using a prone-positioning support, designed to be particularly comfortable, so that real time in "face-down position" in hours per day could be increased significantly. Additionally, the contentment of the patient in reference to the available supports and the appearance of complications has been reported.

RESULTS

In particular the real time of "fdp" in hours per day (24 h) varied greatly (SG: 19.5/24; CG: 5.5/24; P < 0.0001). Equivalent results were reflected in the contentment in reference to the available supports (SG: 99%; CG: 25%; P < 0.0001). Postoperative complications such as moderate or severe back-, neck- or headache only were observed in the CG. Development of a postoperative cataract was observed mainly in the non-supported group.

CONCLUSIONS

By placing supports at the disposal of the patients, it is possible to improve significantly the compliance after surgery. To succeed in using the prone position also at home it is necessary to supply the patient with a support which is comfortable, cheap and easy to handle.

[Health promotion within health care - analysis of employees' smoking habits, consequences for patient care and resources for future smoking cessation initiatives]

Smoking is still one of the most dangerous and avoidable health risks. This study "Healthy air at work" analysed smoking habits, state of change, the influence of the diagnosis F.17.0 in patient treatment and estimation of subjective workloads and personal resources in health-care workers. Almost 2 000 questionnaires were analysed. 19.9% of this study population were smokers, while 26.4% were considered to be heavy or very heavy smokers. Half of the current smokers were willing to change, while the majority had already tried to quit multiple times. The most important motive to stop smoking was fear of consequences (44.4%), followed by other reasons (42.3%) (e. g., pregnancy) and expenses (33.9%). Protection against second-hand smoke was estimated mostly as very relevant, especially for patients. Being a role model in terms of tobacco consumption seems to be important for health-care workers. 61.3% of all health-care workers stated that patients' nicotine dependency had been diagnosed and out of these 46.5% say it is a relevant factor in therapy. 60% of all interviewed employees evaluated themselves as working quantitatively under heavy and very heavy workloads, while 20% had to deal with high qualitative challenges. In terms of future work ability and personal resources 75% were considerably optimistic. We did not find any relation in terms of workloads and smoking habits. Rather few health-care workers used nicotine replacement therapy during former cessation trials. Health-care workers could play an important role in the treatment and prevention of smoking dependency. This potential is not used to its full extent up to now.

[Combined pharmacosurgery as treatment for diabetic macular edema: core pars plana vitrectomy and intravitreal injection of bevacizumab and triamcinolone]

BACKGROUND

The aim of this work is to report the efficacy of a 1.5 mL core pars plana vitrectomy (cppV) combined with isovolumetric substitution with 1.25 mg bevacizumab and 8 mg triamcinolone for the treatment of diabetic macular edema (DME).

METHODS

Data of 73 eyes (60 patients; mean age: 65.4 ± 10.4 years) with diabetic macular edema were retrospectively analysed. Main outcome measures were changes in visual acuity, central macular thickness (CMT) and the need for re-intervention and further treatment modalities, i. e., laser photocoagulation (LPC) or pars plana vitrectomy (ppV). Study eyes were assigned to one of three groups: non-proliferative diabetic retinopathy without ischaemic maculopathy (NPDR I. M.; group I; n = 38 eyes); NPDR with I. M. (group II; n = 17 eyes); proliferative diabetic retinopathy with or without I. M. (group III; n = 18). Mean follow-up times were 9 weeks (T1), 25 weeks (T2) and 44 weeks.

RESULTS

Preoperative mean VA was 0.69 ± 0.4 logMAR. A statistically significant increase in mean VA was observed in all study eyes at 2 months after the initial operation (T1; 0.51 ± 0.22 logMAR; p < 0.01). This remained stable at T 2 (0.52 ± 0.33 logMAR; p = 0.6) and T 3 (0.55 ± 0.35 logMAR; p = 0.99). At baseline mean VA was 0.52 ± 0.21 logMAR in group I, 0.99 ± 0.5 logMAR in group II and 0.77 ± 0.42 logMAR in group III. At T 1 (2 months) the VA change was statistically significant in group II (0.64 ± 0.18 logMAR; p < 0.05) only. In contrast, group I had a highly significant VA gain after 6 months (0.36 ± 0.16; p < 0.01). Patients with PDR (group III) had a non-significant VA gain at T 1 (0.53 ± 0.24; p = 0.08) and remained stable at T 2 and T 3. The mean central macular thickness (CMT) in all study eyes decreased significantly from 393.7 ± 120.6 µm to 269.7 ± 100.2 µm (delta -28 %; p < 0.01) at T 1. Thereafter CMT slightly increased but, on the whole, remained stable at that level. Retreatment with the intravitreal combination therapy was performed in 20 of 73 eyes (27.4 %). Laser photocoagulation was only carried out in more than half of the eyes with PDR (10 / 18; 55.6 %). An increase in IOP was noted in 12 / 73 eyes (16.4 %) at different follow-up, and was controlled using topical medication. Systemic side effects were not reported.

CONCLUSION

Our data show that the majority of the study eyes maintained or improved their visual acuity after pharmacosurgical therapy. Furthermore we observed a reduction of the central macular thickness in almost all study eyes. Only few retreatments and other treatment modalities were needed during the follow-up period. This combind pharmacosurgical treatment may supplement current treatment standards like laser photocoagulation, classical pars plana vitrectomy or intravitreal monotherapy for DME.

Luminescence Activation of Porous Silicon by Post-Anodization Treatment

We prepare “nonluminescing” porous Si by electrochemical etching (50 mA/cm2 in 50% HF diluted 1:1 with ethanol) of 1 Ω(100) p-type wafers in the absence of light in order to study the subsequent luminescence activation by postprocessing. The treatments are: photochemical etching, ageing under ambient conditions, thermal oxidation. The study reveals remarkable inhomogeneities in the depth distribution of the luminescence and allows us to comment on the relative importance of particle size, spin density and chemical composition for the luminescence.

Fast Photoluminescence from Porous Silicon

Time-resolved studies of the visible photoluminescence in porous silicon with three different coverages of the internal surface are reported. We use aged, naturally oxidized porous Si (oxihydride), rapid thermal processed material (oxide) and samples stored in HF (pure hydride). A new, fast luminescence band in the blue-green spectral range and with response time less than 100 ns is observed at room temperature in each of the samples, although with different intensities. The observations prove that this is not an oxide-defect luminescence. We speculate on mechanisms for the origin of the fast luminescence in nanometer-size crystallites of Si.

Some Perspectives on the Luminescence Mechanism Via Surface-Confined States of Porous Si

We elaborate on the explanation of radiative emission involving surface-confined states on the nanocrystallites of porous Si. After reviewing the evidence for the existence of such states, we give a model description of the origin of visible luminescence in porous Si. The model accounts for different spectral luminescence bands with distinct energies and relaxation times.

Prospects for Infrared Electroluminescence From Porous Silicon

Efficient visible luminescence from porous Si requires the 3-dimensional confinement of charges in structures with typical ∼3nm size. Such microporously etched Si acts as an intrinsic wide-gap material and is highly resistive. The material does not have the good transport properties consistent with an efficient electrical excitation. We instead suggest to employ mesoporously etched, p+-type Si with its better conductivity in electroluminescence application. The material luminesces in two spectral bands centered about 0.8eV and 1.0eV in the infrared. Both emissions originate from surface-bound states. We report on the temperature dependence of luminescence, on transport and first attempts to generate infrared light by the injection of electrical current.

Models and Mechanisms for the Luminescence of Porous Si

Explanations for the efficient, visible luminescence of porous Si fall broadly into three categories. At the extremes are the pure quantum-well point of view and the molecular agents hypothesis. We make here the case for a model in which the dominant absorption characteristics are those of a quantum well, but luminescence occurs via boundary states on the nanocrystalline particles. This so-called “smart quantum-well” mechanism accounts for the multiple emission bands of porous Si in a natural way. In particular, the infrared band is assigned as an electronic transition to a deep level. From this we determine the conduction band shift with particle size.

Electroluminescence Device Perspectives of Si+-Implanted SiO2

Thermal oxide layers on Si which have been implanted with Si conduct electrical current and emit light. The electroluminescence effect (EL) has an efficiency which is comparable to the best values that have been reported for the porous Si based devices. Generally, the EL spectrum differs substantially from the photoexcited luminescence. It is linked with that excited by external high energy electrons in cathodoluminescence (CL) experiments. We suggest to consider the effect as internal CL. Based on studies of transport and EL characteristic we evaluate the possibilities of an electroluminescent device based on such layers.

Composition and Morphology of Luminescent Porous Si

Using thermal effusion of H together with a weighing of the remaining Si we determine the composition of luminescing porous Si. From studies of the IR vibration spectrum and its change with effusion we. argue that the H of freshly prepared microporous Si is bound in the dihydride form SiH2. We thus obtain a surface to volume ratio and a characterisicic linear dimension of the porous surface layer. The paper concludes with some observations on photo- and electroluminescence.

Infrared and Visible Emission from Si Layers

We present an experimental study of light emission in silicon devices, mainly MOSFETs, p-i-n diodes, and MIS structures. The special analysis shows important features below as well as above the gap, indicating the type of mechanism responsible for the light emission. Striking differences we found between planar and vertical-type structures.

Improvement of the Luminescing Behaviour of Simmplanted SiO2 Films

In previous work we reported on the observation of continuously tunable photoluminescence in Si+-implanted SiO2-films with moderate intensities. In this paper we demonstrate improved performance of such samples. The photoluminescence intensity increases abruptly up to two orders of magnitude when the anneal temperature is elevated to values higher than 1000…1100°C. This strong photoluminescence degrades less than that of porous silicon. Very fine tunability in the spectral range from 2.1 eV to 1.3 eV is achieved in samples implanted with a graded dose. In the analysis of the results we try to distinguish between the contributions of the Si-nanocrystals and of the oxide related defects.

The Oxidation Behavior of Silicon Nanocrystals in the Submonolayer Region

Fourier transform infrared spectroscopy is used to determine the time evolution of oxygen incorporation onto the surface of silicon nanocrystals. Oxygen concentrations up to one monolayer are investigated. The temporal progress of surface oxidation of Si nanocrystals in porous silicon shows a linear dependence on the square root of the oxidation time. This is similar to the oxidation of bulk Si and mesoporous silicon.

Domain Structure of Poled Ferroelectric (111) PZT (PbZr0.25Ti0.75O3) Films

Films of (111) oriented self-polarized, tetragonal ferroelectric PZT crystallites on (100)Si/SiO2(250 nm)/(111) Pt (50 nm) have been investigated by STM, AFM and SAXS. After metallization of the PZT surface with a Cr-Ni film (5.2 nm thickness) or a Ti film (5.0 nm thickness), single domains were visible on the metal surface by STM measurements as parallel stripes. The lamellar stripes had a width of 10.5 – 25.2 nm and a vertical corrugation of 0.9 – 3.0 nm at the intersection line of the domain walls with the crystallite surface.

High resolution AFM with EBD supertips on unmetallized samples revealed areas of typically several µm in diameter showing crystallites with perfectly parallel aligned (90°) domains of 10 - 15 nm width with their boundaries along {110} planes. Single domain walls were visible as a trace on the surface by a negative corrugation effect of 1.0 – 1.5 nm. This corrugation is assumed to be a reflection of the strain distribution normal to the surface. Furthermore, coherency (oxygen) defects are accumulated at the interface between 90 ° twin domains.

SAXS investigations allowed to estimate a mean value of domain thickness of 17.5 nm. Exertion of stress (5.1 104Nm−2) to the film resulted in an increase of domain width by ∼1%.

Ex-vivo human lung tumor model: use for temperature measurements during thermal ablation of NSCLC

PURPOSE

In the present study we used an ex-vivo human lung cancer model to compare temperature diffusion during thermal ablation using one laser fiber to that of a two-fiber approach. Furthermore, we examined whether there was a difference between temperature diffusion in normal lung tissue and tumor tissue during laser ablation.

MATERIALS AND METHODS

48 resected lung specimens containing non-small cell lung cancer were connected to a perfusion/ventilation apparatus and treated with 1 (22 specimens, group 1) or, in a second experiment, with 1 (13 specimens, group 2) or 2 (13 specimens, group 3) laser fibers. During tumor ablation, temperatures were measured interstitially every 5 sec. Laser ablation was followed by the taking of samples of 13 specimens for histological examination. For comparison we performed laser ablation in 7 specimens with normal lung tissue.

RESULTS

Laser treatment and temperature control were technically feasible in all samples. Thirty min after starting laser ablation with 1 fiber, a temperature of 61 ± 17 °C was achieved in group 1 at a distance of 10 mm from the laser fiber and a temperature of 74 ± 11 °C was achieved in group 2 (p = 0.1). In the middle between two active laser fibers placed 20 mm apart, a temperature of 93 ± 7 °C was achieved. The temperature reached in normal lung tissue after 20 min of laser ablation was 77 ± 15 °C at a distance of 10 mm from the laser fiber.

CONCLUSION

The ex-vivo model allowed performance of laser-induced thermal ablation in the perfused and ventilated lung. The use of two laser fibers increases the achieved temperatures significantly (p < 0.05). Temperatures reached in normal lung tissue were as high as in tumor tissue (p = 0.24).

Extraction of nutrients from foam in a membrane activated sludge system

This study investigated the feasibility of treating the foams generated in enhanced biological phosphorus removal processes with the microwave-enhanced advanced oxidation process to reduce solids and solubilize nutrients for recovery purposes. It was found that more than half of the total chemical oxygen demand was solubilized during the treatment with just a small dose of hydrogen peroxide, signifying effective destruction of foam solids. Significant solubilization of phosphates, volatile fatty acids and ammonia was also observed, along with the release of metals contained in the foam, including calcium, potassium, and magnesium, which thereby represents additional potential benefits for nutrient recovery via subsequent crystallization processes. Since the solids content of foam is typically high, pretreatment for thickening sludge solids is not necessary prior to the use of microwave-enhanced advanced oxidation processes. As a result, this also offers further potential for reduction of energy costs. The process could be an efficient method for the removal and control of foam and the recovery of all available phosphorus at the same time.