Material requirements for the adoption of unconventional silicon crystal and wafer growth techniques for high‐efficiency solar cells

Silicon wafers comprise approximately 40% of crystalline silicon module cost and represent an area of great technological innovation potential. Paradoxically, unconventional wafer‐growth techniques have thus far failed to displace multicrystalline and Czochralski silicon, despite four decades of innovation. One of the shortcomings of most unconventional materials has been a persistent carrier lifetime deficit in comparison to established wafer technologies, which limits the device efficiency potential. In this perspective article, we review a defect‐management framework that has proven successful in enabling millisecond lifetimes in kerfless and cast materials. Control of dislocations and slowly diffusing metal point defects during growth, coupled to effective control of fast‐diffusing species during cell processing, is critical to enable high cell efficiencies. To accelerate the pace of novel wafer development, we discuss approaches to rapidly evaluate the device efficiency potential of unconventional wafers from injection‐dependent lifetime measurements. Copyright © 2015 John Wiley & Sons, Ltd.     

0.75 V supply nanowatt resistorless sub-bandgap curvature-compensated CMOS voltage reference

This work presents a resistorless self-biased and small area sub-bandgap voltage reference that works in the nano-ampere consumption range with 0.75 V of power supply. The circuit applies a curvature compensation technique that allows an extended temperature range without compromising the temperature stability. The behavior of the circuit is analytically described, and a design methodology is proposed which allows the separate adjustment of the bipolar junction transistor bias current and its curvature compensation. Simulation results are presented for a 180 nm CMOS process, where a reference voltage of 469 mV is designed, with a temperature coefficient of 5 ppm/°C for the ?40 to 125 °C extended temperature range. The power consumption of the whole circuit is 16.3 nW under a 0.75 V power supply at 27 °C. The estimated silicon area is 0.0053 mm².     

Transmission line routing for reduced external field disturbance

When immersed in a disturbing electromagnetic field, electronic systems are subject to interference due to the energy injected by the external field into the system through the electronic units and, especially, through the transmission lines connecting units one another. The issue of reducing the unwanted energy injection through connecting transmission lines is addressed in this contribution from the point of view of the routing, i.e. of the disposition of the connecting lines that minimizes the injection. The problem is formulated as an optimization problem, dealt with by the simulated annealing minimization technique combined with an efficient way of computing the field coupling to the lines. Results are reported for various cases, and the relation between the characteristics of the interfering field and the efficiency of the reduction is discussed.     

An improved technique for prolonged arterial catheterization in infants and children

Arterial catheterization for blood gas analysis and direct monitoring of blood pressure in infants and children can be attended by a variety of complications, which limit its use to short periods of time. An improved technique, consisting of elimination of stopcocks, the use of a continuous flushing system adapted for infants and children, and meticulous care of the system, was used in 57 children whose ages ranged from the neonatal period to 16 years. The mean duration of cannulation was 5.5 days (range, 1-31 days). All but one of the catheters were functional at the time of discontinuation. There were no thromboembolic phenomena, local or systemic infections or accidental bleeding. We feel that our approach to prolonged arterial cannulation can be an extremely valuable aid in the management of critically ill children.     

Persistent obstructive jaundice, cholangitis, and biliary cirrhosis due to common bile duct stenosis in chronic pancreatitis

Long strictures of the intrapancreatic portion of the common bile duct were found in 6 patients with chronic pancreatitis. These strictures were responsible for painless obstructive jaundice, recurrent cholangitis, secondary biliary cirrhosis, and chronic abdominal pain difficult to distinguish from that caused by pancreatitis. Endoscopic retrograde cholangiopancreatography and intraoperative cholangiography were invaluable in making the diagnosis and in planning surgical correction. Decompression of the biliary tree by anastomosis of the gallbladder or common duct to the small intestine completely relieved symptoms and allowed liver function to improve significantly. Common duct stricture as a complication of chronic pancreatitis should be considered in the differential diagnosis of extrahepatic biliary obstruction and whenever surgical treatment of chronic pancreatitis is contemplated.     

Continuous dynamic monitoring of pressure and flow patterns during assisted ventilation

On curettage, done in a 39 year old patient because of metorrhagia, a peanut-sized nodule was scraped away from the endometrium. Histologically it consisted of a jumble of irregularly shaped portions of normal appearing embryonal cartilage, of tortuous thick-walled vessels, of twisted bundles of nerves of ducts of respiratory and intestinal epithelium, and of sheets of hornifying skin. The haphazard disarray of tissues supported the notion that the lesion was not a remnant of a malformed embryo. Step-sections through the lesion revealed no traces of placental villi or decidua in the surrounding endometrium. The following were considered as possible origins of the teratoma: 1. displaced germinal cells, 2. retention of pluripotent müllerian epithelium, 3. overaged or blighted ovum. The latter seems most compatible with the histological findings.     

The effect of pantothenic acid on the diet of growing chicks on energy utilization and body composition

Two experiments were conducted to investigate the effects of varying levels of pantothenic acid on the efficiency of energy utilization and changes in body composition of the growing chick. The results indicate that a pantothenic acid deficiency does not interfere with the chick's ability to obtain metabolizable energy from the diet. The data do show that the efficiency of energy utilization and body composition were markedly affected when chicks were fed diets deficient in pantothenic acid. In both experiments, protein, fat and energy stores were significantly reduced when pantothenic acid-deficient diets were fed. Increased estimates of heat increment per gram of diet were observed when levels of pantothenic acid below the N.R.C. (1971) recommended level of 10 mg. per kg of diet were fed.     

Correlation between morning urine estriol concentration and 24-hour estriol excretion

In an attempt to circumvent the need for 24-hour urine collections for estriol analyses in assessment of fetal status, the possibility of using morning urine samples was investigated. Results indicate 1) good correlation between 24-hour estriol excretion and morning estriol concentration, and between corresponding E/C ratios, 2) similar morning and 24-hour estriol concentrations, 3) high dependence of estriol and creatinine excretion on 24-hour urine volume but not on morning volume, 4) larger variations in 24-hour than in morning urine volume, and 5) better consistency of values in morning than in 24-hour samples in pathologic pregnancy. The use of serial morning urine concentrations at least as an outpatient monitoring procedure is suggested.     

Selective isolation of reversible cold sensitive variants from Chinese hamster ovary cell cultures

The fine structure and cellular associations of the large pigment cells (LPC's) of the compound eye of the house fly were studied with high voltage and conventional electron microscopy. Depending on the sector of the compound eye, the facets are either rectangular or hexagonal. The underside of each facet has indentations exactly aligned with those on top into which inserts an angulated sleeve of LPC's. Under the rectangular lens facet 6 or 8 small compact (in cross section) LPC's join four elongate LPC's. Clusters of compact cells alternate in this ring with elongate ones. Compact cells compress together and become quadrangular (in cross section) several microns below their insertion into the lens and form "building block" corners while elongate cells form "side rails" for the rectangular type of distal pseudocone enclosure. Beneath hexagonal facets all LPC's are rather elongate with out corner cells. In both facet types LPC's enclose the pseudocone for a longitudinal distance of 4 mum and then are displaced as bordering cells by a sleeve of two corneal pigment cells (CPC's), each of which encloses half of the proximal pseudocone. For the following 6 mum of longitudinal distance these concentric sleeves of CPC's and LPC's form a double layer around the pseudocone. At about 10 mum below lens base the two sleeves separate; LPC's become attenuated and extend cable-like to the basement membrane and CPC's enclose the proximal pseudocone, Semper cells and distal retinula. The junction between lens and LPC's has critical structural value in that (1) this is the sole anchorage to the lens by the lengthy remainder of the ommatidium, and (2) LPC's enclose the semiliquid pseudocone in the most distal portion of the pseudocone. In addition to vertical support, the LPC's send out numerous lateral processes that make structural contact among themselves, with the corneal pigment cells and the photoreceptor cells. The structural features of this array are discussed relative to possible physiological roles.