HVST scares the heck out of me. Bought 40k shares of QCC today. Another good day for us! I'm hoping everyone or most of you gain some nice SP and congrats for all those who realized their gain today I'm hoping there will be some healthy consolidation either tomorrow or sometime next week since this gains is scaring me.
N seems too volatile. Doesn't know if it's coming or going at this point. From what i've experienced in the stock market in the past, those are red flags for me to stay away. I got lucky that it bounced back up after the second halt was lifted. Someone sold a boatload of shares, if that doesn't speak to the NR tomorrow, i don't know what does. Its gradual minor gains are a sign of a very healthy stock. D When the macrophage layer regenerates, B cells can again participate in humoral immunity.
Activation of toll-like receptors leads to the production of inflammatory cytokines, DC maturation, and DC migration. Thus, inflammation, rather than particulate-carrying lymph per se, is needed for this dramatic breakdown in lymph node architecture. Remarkably, lymph nodes can expand to at least fold their original volume within Disruption of the SCS macrophage layer was attributed both to macrophage death and to macrophage migration into the interior of the node.
Because most. If this event is simply a consequence of macrophage disturbance by incoming DCs as they traverse the SCS floor, then migration would have to be remarkably equitably distributed above areas of the node that typically do not house large numbers of migratory DCs e. Alternatively, rather than displacing macrophages, incoming DCs might signal them to migrate as well. How well does a fragmented SCS macrophage layer function in generating an antibody response to secondary infections?
Not very. Delivering an activating signal for the receptor to disrupt the SCS macrophage layer without activating the transferred B cells decreased B cell capture of subsequent lymph-borne antigen by a factor of Further, B cells responding to secondary infection after SCS macrophage disruption generated diminished numbers of germinal center B cells and fewer antibody-secreting cells.
The evolutionary advantage of reduced responses to temporally proximal secondary challenges is puzzling. Perhaps disrupting SCS macrophage function focuses immune responses on the primary pathogen or plays an essential role in this response. Indeed, the centripetal movement of pathogenladen macrophages in the lymph node could be an important source of antigen for follicular DCs, driving the development of B cells antibody affinity maturation. A nonmutually exclusive possibility is that, because inflammation alone can trigger SCS macrophage disruption and shut down antibody responses, this phenomenon may minimize autoimmune responses that develop after lymph drainage of self-antigens that are liberated during chronic inflammatory responses.
Gerner et al. Hildner et al. Heath, F. Carbone, Nat. Norbury et al. Junt et al. Hickman et al. Phan et al. Iannacone et al. Kastenmller et al. Chyou et al. Acton et al. Taking temperature at the nanoscale A local probe technique can determine temperature with nanometer-scale resolution By Christian Colliex. However, the definition of temperature is not at all obvious, as it is now described as a statistical quantity given by the rate of change of entropy with respect to the internal energy of a system with volume and number of particles held constant.
This is by itself not an easy concept to grasp. In addition, determining temperature raises thermodynamical questions when considering systems with further and further reduced dimensions 1. Consequently, measuring temperature at the nanoscale constitutes a challenge in many fields of science and technology. On page of this issue, Mecklenburg et al. As even smaller scales are considered, it is also important to use a noninvasive geometry, avoiding the introduction of a temperature gradient between the thermometer and the material to be measured.
Several approaches describe promising routes to nanoscale thermometry. They markedly depend on the environment under study inorganic versus organic , the temperature range of concern, and the required sensitivity in position and in temperature. As an example, for nanometer-scale thermometry in a living cell, the temperature dependence of the electron spin resonance signal associated with the nitrogen-vacancy color centers in nanodiamonds was measured 3.
The transmission electron microscope TEM is the preeminent instrument for. Consequently, temperature indicators on a specimen prepared as a thin foil have been sought in the different signals images of atomic structure, lattice parameters in diffraction patterns that TEMs deliver, but so far without practical development.
Electron energy-loss spectroscopy EELS is another important channel of information. As early as , Watanabe 4 pointed out that the energy of the bulk plasmon line that is, the collective response of the quasi-free electrons in the solid should depend on the temperature through the associated volume expansion and consequent reduction in electron density.
But this was undetectable by his instrument at that time. More recently, the volume plasmon energy in aluminum was measured over the range of temperature between and C, with a high-resolution energy-loss spectroscopy TEM 5.
Furthermore, in these early studies, the spatial resolution was not mentioned, although Seah and Smith 6 argued for the use of plasmons as quanta for microregion tem-. In a scanning TEM STEM environment, they measure the value of the energy loss associated with the excitation of the plasmons, for each position of the primary electron probe on the specimen. The recorded EELS spectra encompass both the zero-loss peak and the plasmon peak at Consequently, a specific procedure for handling the data has been established: It consists in measuring the center of the plasmon peak, best-fitted to a Gaussian curve, and deducing from its relative variation with respect to a reference spectrum, recorded at temperature T0, the associated change in temperature T T0.
E-mail: christian. Getting the temperature spot-on. The chain of components from the electron beam source in the electron microscope to the display of the temperature of a nanoscale area of the specimen. Hartmann, G. Mahler, O. Hess, Phys. Kucsko et al. Watanabe, J. Abe et al. Electron Microsc. Tokyo 41, Seah, G. Smith, J. Krivanek et al. Argentero et al. Our skewed sense of space The distribution of neuron activity reveals an organization that supports the brains spatial mapping capacity By Gyrgy Buzski.
A specific location will activate a set of neurons called place cells to represent the particular place. What happens as the number of environments encountered increases? Does the hippocampus continually create and store distinct independent maps for each locale, or can place cells be recruited for more than one map to generalize across locales? It appears that both mechanisms contribute in unique ways. At any given position of space, a subset of hippocampal pyramidal cells is active hence they are called place cells , and the firing fields of single neurons place fields can be regarded as units of spatial representation 1.
Collectively, the active sets of place cells track the position of the animal in the environment, and thus they are hypothesized to provide a code for space. But the exact nature of this code is unknown. Several overlapping stories emerged recently about the statistical structure of hippocampal neuronal activity firing patterns and its relationship to coding for the environment The activity of place cells when an animal rat experiences a small, large, new, or familiar environment demonstrates that although the majority of these neurons have single place representation, a small minority can have many see the second figure.
Analyses of the observed skewed distribution of place fields and other log-like features of the firing patterns of hippocampal neurons offer a link between physiological organization and the long-known Weber-Fechner law of psychophysics, which describes our subjective perceptions on a logarithmic scale.
Accordingly, when the stimulus strength is multiplied, the strength of our perception is only additive. To examine the relationship between neuronal firing patterns in the hippocampus and the nature of representation of the environment, rats were tested in a familiar open field, a linear maze, and a radial arm maze.
Although the majority of CA1 and CA3 pyramidal neurons had single place fields, a small fraction fired at multiple locations 2. Thus, both the majority and the minority of hippocampal neurons tiled the environments and the distribution of space coverage by individual place cells was strongly skewed see the second figure. The withinplace field firing rates of individual neurons were also skewed and followed a lognormal form i.
In turn, firing rates correlated with both the number and size of place fields 5. In a given environment, only a fraction of pyramidal neurons are active. Will every. Mixed messages. Neurons with multiple place fields have higher firing rates than the majority of neurons with single place fields. Thus, neurons downstream of the hippocampus receive a mixed messagethe majority of weakly active neurons convey information about the distinctness of the environment, whereas the strongly firing minority suggests similarity.
Another recent study explored this question by training rats to run an expandable maze track with lengths of 3, 10, 22, and 48 m in the same large room 3.
Place cells active on the short tracks could form additional place fields for larger tracks, as new place cells were recruited from the pool of silent hippocampal cells. The number of fields formed by the CA1 pyramidal neurons was strongly skewed: A few neurons had many fields, whereas many neurons had only one or none.
E-mail: gyorgy. The authors extensively describe the sources of errors, both of a statistical nature at different stages of the data processing signal, plasmon energy, temperature and of an intrinsic nature due to the specimen itself nonhomogeneity of the specimen, role of gain boundaries, influence of thickness variations. They also justify the noninvasive character of their thermometer, noting that the current in the electron probe should not provoke an appreciable temperature rise in a thermal conductor about nm thick.
The technique paves the way for a more thorough investigation of the factors governing the spatial resolution, as it distinguishes those contributions related to the measurement technique delocalization arising from the use of a high-energy electron beam from those associated with the quantity temperature under measurement depending on the local transport of heat via electrons or phonons.
In the case of high-angle impact scattering of incident electrons on the nuclei of the specimen, the same type of data processing as that used by Mecklenburg et al. To distinguish 12C from 13C, for instance, it would be necessary to measure shifts of a few millielectron volts on the center of characteristic peaks situated in the tens of millielecton volts loss range. The work of Mecklenburg et al.
In particular, the combination of fabrication techniques for devices of smaller sizes and STEM instruments with aberration correctors for the probe more current in a probe of given size and with monochromators with typical meV energy resolution giving access to the natural width of the involved excitations could enable fundamental studies of the quantum aspects of heat conductance. Skewed distribution. The number of place fields per neuron place cell in the hippocampus shows a skewed distribution with most place cells having none or one place field, whereas a minority have several place fields.
This distribution is present in an open environment shown as a linear maze , radial arm maze, large room [presented as linear tracks of increasing size in a single room 3 ], or in multiple rooms [new or familiar 4 ]. In another study, investigators asked whether independent place cell codes are present in multiple environments 4.
Rats were placed in one familiar box as well as in 10 new boxes, each placed in a different room. Most CA3 pyramidal neurons fired only in a single box, but a small minority fired in all or multiple boxes, showing a lognormal distribution of the overlap of neuronal activity in the different rooms. Overall, these studies 25 demonstrate that the skewed distribution of place fields is a general rule, irrespective of the nature or size of the testing environment.
What could be the advantages of the skewed distributions for coding for space? From the perspective of independent coding 6 , the minority of neurons with multiple place fields are regarded as noise or imperfection of the system. But when other physiological features of the heavy tail-forming minority are also considered, a different picture emerges.
The small subset of place cells is not only more active in multiple environments, but their firing rates are higher, they emit more spike bursts i. The higher mean firing rates of the active minority within their place fields correlate with their firing rates during sleep in the animals home cage 5. Furthermore, the diligent minority fires synchronously with other neurons more frequently in all brain states during both sleep and waking than the slower-firing majority and critically, it exerts a relatively stronger and more effective excitation on its targets.
The distribution of the magnitude of collective population firing pattern is also lognormal 5. The consequence of this population organization is that in the physiological time frames of theta oscillations and sharp wave ripples of neuronal activity 4, 5 , approximately half of the spikes emitted by the hippocampal neurons are contributed by the active minority; the remaining half are contributed by the great majority of neurons with single place fields.
This mixed output is what the downstream observer-classifier neurons of the hippocampal output must use to generate action see the first figure. This emerging picture of hippocampal dynamics suggests that neurons at the opposite ends of the distributions may convey different but complementary types of information.
The ever-active minority of place cells may be responsible for generalizing across environments and affords the brain the capacity to regard no situation as completely unknown because every alley, mountain, river, or room has elements of previously experienced similar situations. In many situations,. On the other hand, the majority of less active neurons constitute a large reservoir that can be mobilized 7 to precisely distinguish one situation from another and incorporate novel ones as distinct.
The distribution of synaptic strengths, neuron firing rates, population synchrony, axon conduction velocity, and macroscopic connectivity of neuronal networks throughout the brain displays a skewed, typically lognormal form 8, 9. The relationships among these multilevel skewed distributions need to be explored to better understand network operations that underlie brain function. An important practical implication of these recent studies is that analyzing physiological data by parametric statistics is a violation because most variables are skewed.
The theoretical implication is that brain dynamics supported by lognormal statistics may be the neuronal mechanism responsible for Weber-Fechner log perceptions, including our sense of space. OKeefe, L. Press, Oxford, Mizuseki et al. Rich, H.
Liaw, A. Lee, Science , Alme et al. Mizuseki, G. Buzski, Cell Rep. McNaughton et al. Dragoi, K. Harris, G. Buzski, Neuron 39, Buzski, K. Mizuseki, Nat. Markov et al. The two groups carried out transcriptome-wide mapping of m6A sites m6A-seq in ESCs using a specific antibody against the modification.
These data confirm previous By Hendrik G. Stunnenberg, plants, to yeast, to mammals 5. The mark is deposited by a hetcell types and across many species 7. The global changes in gene expression, erodimer of methyltransferase-like 3 and 14 largest proportion of m6A sites are similar some of which are driven by epigen Mettl3 and Mettl14 and can be removed between ESCs and their differentiated linetic alterations, often including methby the RNA demethylase enzymes FTO and eages; only a small number of transcripts ylation of DNA.
However, until recently, it reare methylated in a cell-typespecific man ESCs have been used to decipher mained unclear whether m6A has any funcner.
Nonetheless, in the absence of methods many of the critical factors underlying celltional role in stem cell homeostasis. Mouse ESCs exist in several Geula et al. New research now reveals another in vitro or in vivo [results that are contrary Both Geula et al. Geula et al.
They showed that the modithan DNAat position six of the adenosine genetically modified mice lacking Mettl3 fication is negatively correlated with RNA base m6A. The majority of pluripo 4 , show that m6A is involved in regulating ripotency markers e.
These observaFor ESCs to commit to differentiation, the ity and translation. Depletion of m6A results in elevated across many different species, ranging from commitment. Geula et Nijmegen, Nijmegen, Netherlands. A A Waddington epigenetic landscape illustrating that ESCs can regulating RNA stability, take on different cell fates that have different epigenetic states shown as valleys. In the absence of m6A, RNA abundance of pluripotencycome of m6A methylation on promoting genes increases, which impairs differentiation.
Thus, differential cell- and state-specific expression or binding of readers may appreciably affect the functional readout of the m6A methylome. Currently, it is not known whether other protein domains can bind to m6A or whether different YTH-domain proteins display differential binding depending on the sequence context of m6A sites. Moreover, Geula et al. The findings of Geula et al. Whether and how RNA methylation regulates homeostasis of adult stem cells should be a fertile area of investigation.
For example, genetic variations in the m6A-demethylase FTO have been linked to cancer, obesity, and metabolic disorders Whether aberrant RNA methylation or defects in writers, readers, or erasers affect differentiation of adult stem cells and lead to disease are exciting questions for the field.
Taken together, these studies highlight a role for m6A as an important posttranscriptional regulator of cell-fate decisions. It is interesting to note that there are about different covalent RNA modifications, and only now are we beginning to uncover a functional role for some of them. It might be that m6A represents the tip of the iceberg in a new era of epitranscriptomics.
Ying et al. Marks et al. Batista et al. Fu et al. Wang et al. Cell Biol. Schwartz et al. Xu et al. Loos, G. Yeo, Nat. Waddington, Organisers and Genes Cambridge Univ. Press, Cambridge, The coordination chemistry of nanocrystal surfaces The luminescence and electronic properties of inorganic nanocrystals depends on surface-layer structure By Jonathan Owen. However, the surfactant ligands that stabilized NCs also influenced their electronic structure and optical properties.
Encapsulating the NC cores within an insulating inorganic shell reduced the effect of surface structure on charge recombination 2 and forced the radiative recombination of photoexcited charges.
These structures greatly increased the photoluminescence quantum yield PLQY and enabled their recent use in liquid crystal displays. However, PLQYs of core-shell nanocrystals remain sensitive to their surfaces and if NCs are to be useful within electrical devices, such as photovoltaic PV cells, the complex relation between their surface structure and their frontier orbital structure must be better understood.
Surface atoms of NCs have lower coordination than bulk atoms, which results in weaker bonds that in turn create electronic states within the semiconductor band gap that trap photoexcited charges before they can radiatively recombine.
Surfactant ligands coordinate to surface atoms, which strengthens their bonding, and passivates these midgap electronic states, and enables luminescence. Thus, tailoring the ligand shell for its interactions with the surrounding medium, be it cellular cytoplasm or the conducting matrix of a light-emitting diode LED , will influence the surface-derived electronic structure and the optical performance.
Similarly, surface trap states define the lowest energy path for charge transport 3. The influence of ligation on electronic structure makes surface coordination chemistry critically important in NC science. Density functional theory DFT simulations of surface ligand interactions can be informative, but experimental structures have only.
Surface-ligand chemistry. A Examples of several ligand exchange reactions are shown. B The coordination of different types of ligands in Greens formulation 4 to metal-chalcogenide nanocrystals NCs, such as cadmium selenide are illustrated. R is an alkyl group; Bu is n-butyl. Untangling the atomic structure of NC facets requires methods beyond the ones used with bulk singlecrystal surfaces, many of which work well only in ultrahigh vacuum and with well-ordered, flat surfaces.
E-mail: jso columbia. Early investigations of II-VI NCsin particular, cadmium selenide synthesized in tri-n-octylphosphine oxideconcluded that the dominant ligand type is a datively bound, neutral donor, a so-called L-type ligand see the figure 5. Langmuir-like adsorption should result that could be manipulated according to Le Chateliers principle: If the NCs are placed into a solution containing a much greater concentration of a new L-type ligand, the original ligands should be displaced, regardless of their relative binding affinity.
However, early. The influence of ligation on electronic structure makes surface coordination chemistry critically important in nanocrystal science. Several groups then explored ligand exchange reactivity by systematically measuring the effects of ligands on PLQY These studies revealed both a complex underlying surface coordination chemistry and a complex relation between PL and ligation that remains a difficult and central topic in colloidal crystal science.
In recent years, it has been realized that L-type ligands are not the primary mode of surface-ligand stabilization. In a landmark study of lead selenide NCs, Moreels et al. They concluded that the NC surfaces are covered by a monolayer of lead atoms.
Solution 1H and 31P nuclear magnetic resonance NMR spectroscopy revealed that a shell of anionic or X-type ligands provided the charges needed to balance the cationic charge of a metal-rich NC The anionic ligandcationic NC description helped explain the difficulty encountered in early exchange studies and opened the door to the design of new reactions that maintain the charge balance between the NC and its X-type ligand shell.
In the past 5 years, successful ligand exchange studies have used a modified Le Chateliers These strategies have led to dramatic improvements in the charge-transport mobilities of NC field-effect transistors and record efficiency of NC PV cells More recently, NMR spectroscopy revealed that the surface metal ion layer that enriches the NC formula is labile and can be displaced as a complex along with its associated ligand anions, or Z-type ligands The NC stoichiometry is concentration dependent and controlled by the medium in which the NC is suspended.
The same study also reported a dramatic and well-behaved dependence of the PLQY on the surface coverage of metal carboxylate complexes. Absent better understanding of these issues, practical control over the composition and structure of metal surfactant complexes that bind the NC surface will remain erratic.
Batch-to-batch variability is typical in the most common methods used to synthesize NCs and variations in the NC composition arise from methods that afford uncontrolled reactivity or terminate the precursor conversion prematurely to obtain a desired size.
These effects are compounded by isolation procedures and standards for sample purity that are largely unstudied. Thus, new synthetic methods are needed that reproducibly prepare and isolate NC with known compositions on a larger scale if the structural origins of NC properties are to approach our understanding of bulk semiconductor crystals.
This level of control will be necessary for NC technologies to impact not only lighting and photovoltaic technologies but also the biological sciences. Murray, D. Norris, M. Bawendi, J. Hines, P. Guyot-Sionnest, J. Nagpal, V. Klimov, Nat. Zherebetskyy et al. Green, J.
Kalyuzhny, R. Murray, J. B , Bullen, P. Mulvaney, Langmuir 22, Munro, I. Jen-La Plante, M. Ng, D. Ginger, J. C , Moreels et al. Owen, J. Park, P. Trudeau, A. Alivisatos, J. Chuang, P. Brown, V. Bulovi, M. Bawendi, Nat. Anderson, M. Hendricks, J. Choi, J. Verhagen, Sander Herfst, Ron A. These incursions of newly emerging HPAI H5 viruses constitute a threat to animal and potentially human health and raise questions about the routes of transmission.
Wild birds of the orders Anseriformes ducks, geese, swans and Charadriiformes gulls, terns, waders are the natural reservoir for low pathogenic avian influenza LPAI viruses. LPAI viruses generally do not cause substantial disease in wild birds and poultry.
Historically, HPAI outbreaks in poultry have been controlled rapidly by methods such as mass culling. These outbreaks were associated with the first recorded cases of human infections with H5 influenza viruses and with spillback of HPAI viruses to wild birds.
Text Review export. Color Picker. Explore Pro. Santos saves time on remote sites. Learn more about Drawboard PDF for enterprise. Get started with Drawboard PDF. Start in your web browser. Thus the device has to be first characterized. The process started by first setting the voltages to their maximum specifications. As long as the chip did not fail, both supply voltages were increased by mV and the KGU was retested.
The flow was repeated for another KGU to verify the result. It is important to label and store every KGU that failed to confirm all failures in the Failure Analysis lab. The voltage for Vdd core was held constant at A2. Again, the test procedure was verified for another KGU.
The third step was to identify the core breakdown voltage. The core voltage of the device under test at the time of failure was marked as the core breakdown voltage B2. The entire flow was then implemented again to verify the result on another unit. Both supply voltages were set to mV below their found breakdown voltages B1 and B2, and the list of the HVST test pattern list was applied.
A sample size of 20 units was used for this test. The sample set of 20 units was also used for this purpose. The failed units were segregated and the voltage levels at the times of failure were noted. If the data showed that repeatability was unsatisfactory, the breakdown voltage characterization must be repeated for a new set of KGUs.
The HVST pattern was executed repeatedly on all units. The rejects were segregated and verified. The procedure was repeated until the entire set passed 3 consecutives times without a single reject.
Burn-in study is required to validate the infant mortality, whereby failure rate must be within the pre-specified requirements. Reliability can be assured if there is no degradation or early wear-out. This study was carried out in the burn-in reduction experiment flow shown in Fig.
It shortens the time required for weak devices to fail during nominal operating conditions tN by stressing them at an acceleration factor A. The equation below describes the relationship between, the time to failure under stress burn-in conditions tS , the acceleration factor A tS for the given time under stress, and the nominal time to failure tN. Hence the acceleration factor for the burn-in conditions must first be calculated.
The rest of the used above parameters can be found from the device specifications sheet. Apart from the voltage acceleration model described in the presented research, employment of appropriate alternative voltage acceleration models is also possible depending on the technology parameters of the device. These models can be found from JEDEC standards [17, 18] as well as from the literature, for example []. Table 3 shows the calculated acceleration factors. Table 3. To reduce the burn-in time to some target duration of t1 hours e.
The results of the study are summarized in Table 4 only the percentage yield is discussed here due to confidentiality.
No fallouts were observed after the hour proof burn-in H13 and H14 , indicating that the there was no degradation in device reliability while the failure rate was within specified requirements. The results taken at point H1 of the experimental burn-in flow were compared with those obtained at the point B2 of the control flow Fig. Table 5 shows the comparison between the yields of the study flow and control flow room temperature tests.
It can be seen that the room temperature test combined with HVST screens out 1. This shows that HVST can effectively screen out weak infant devices compared to a hour burn-in. Table 5 Control Test Flow vs. Since the yields for these two tests are almost similar, it is a good indication that the HVST did not damage good units while stressed the device population well enough to screen out weak infants.
In short, the test results show that the HVST program was both effective and reliable. The least-squares method is generally preferred because it is an effective and computationally simple means to model the complex nature of failures of a product [23].
This plot provides information on ELFR achieved at various burn-in durations. The new burn-in hours can then be calculated based on pre-determined criteria specific to the device such as PPM, confidence level and duty cycle.
This is an extremely valuable outcome of the research. The HVST program was highly effective in screening out weak devices, resulting in a very significant reduction of burn-in time.
Burn-in test is one of the mort popular techniques of accelerated testing in the modern semiconductor industry. In a very significant extend it can provide a form of guarantee on reliability and quality of the final electronic products.
However, the burn-in incurs a high turnaround time and inevitably high cost in testing. The research and experimental results presented in this paper show that the application of HVST combined with the use of Weibull statistical analysis can reduce the burn-in time very significantly while still providing required level of reliability and quality.
Finally, we plan also to look at the possibility of extending our research on HVST and Weibull analysis application to wafer-level burn-in testing in the manufacturing environment. Revision 3. SA Department of Defense.
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