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Magnetically Dominated Strands of Cold Hydrogen in the Riegel-Crutcher Cloud N.M.McClure-Gri?ths,1J.M.Dickey,2B.M.Gaensler,3,4A.J.Green,5and Marijke Haverkorn 6,7ABSTRACT We present new high resolution (100′′)neutral hydrogen (H i )self-absorption images of the Riegel-Crutcher cloud obtained with the Australia Telescope Com-pact Array and the Parkes Radio Telescope.The Riegel-Crutcher cloud lies in the direction of the Galactic center at a distance of 125±25pc.Our observations resolve the very large,nearby sheet of cold hydrogen into a spectacular network of dozens of hair-like ?laments.Individual ?laments are remarkably elongated,being up to 17pc long with widths of less than ～0.1pc.The strands are rea-sonably cold,with spin temperatures of ～40K and in many places appearing to have optical depths larger than https://www.doczj.com/doc/1e9464875.html,paring the H i images with obser-vations of stellar polarization we show that the ?laments are very well aligned with the ambient magnetic ?eld.We argue that the structure of the cloud has been determined by its magnetic ?eld.In order for the cloud to be magnetically dominated the magnetic ?eld strength must be >30μG.Subject headings:ISM:structure —ISM:clouds —ISM:magnetic ?elds —radio lines:ISM
1.Introduction
Recent high resolution surveys of neutral hydrogen(H i)in the Galactic Plane show that the structure of the warm atomic medium varies signi?cantly on arcminute scales.The detailed structure of cold H i,however,is much more elusive.Most of our knowledge of cold H i comes from observations of H i absorption towards continuum sources(e.g.Heiles &Troland2003,2005).Although these measurements are e?ective for determining gas temperature,they have limited applicability to structural studies because they only trace gas along single lines of sight towards an irregularly distributed array of background sources. Another probe of cold H i is H i self-absorption(HISA)towards bright background H i emission.This is not,strictly speaking,self-absorption,but absorption of background H i emission by cold foreground H i.Surveys like the Canadian Galactic Plane Survey(CGPS; Taylor et al.2003)and the Southern Galactic Plane Survey(SGPS;McClure-Gri?ths et al. 2005)have revived studies of HISA,showing that it is a good probe of the structure of cold H i on small scales(e.g.Gibson et al.2000;Kavars et al.2005).Although these studies are able to image HISA over large areas,and have better estimates of the background emission than lower resolution surveys,it remains di?cult to unravel the structure of the cold foreground H i from variations in the background emission.
One of the most famous examples of a large scale HISA feature is the Riegel-Crutcher (hereafter R-C;Riegel&Crutcher1972)cloud in the direction of the Galactic center.The R-C cloud was?rst discovered by Heeschen(1955)in his survey of H i at the Galactic center and he suggested that the cloud was very extended.Subsequent observations by Riegel&Jennings(1969)showed that the cold cloud extends over～40degrees of Galactic longitude and～10degrees of latitude.It has even been suggested that the cloud is part of a much larger structure,Lindblad’s Feature A,spanning the full360deg of Galactic longitude (Lindblad et al.1973).Estimates of the temperature of the cloud show that despite its striking appearance it is not exceptionally cold,with most estimates of spin temperature ranging between35-45K(Montgomery et al.1995;Riegel&Crutcher1972;Riegel& Jennings1969;Heeschen1955).By measuring Ca II lines in the spectra of OB stars Crutcher &Riegel(1974)determined that the cloud is between150and180pc distant.Further Na I observations by Crutcher&Lien(1984)helped constrain the distance to125±25pc,with an estimated thickness of1to5pc.
The R-C cloud provides us with one of the best opportunities for imaging the cold neutral medium(CNM)over a large area.The H i background towards the center of the Galaxy is amongst the brightest anywhere in the Galaxy;this direction provides an ideal bright,high column density background against which to image the CNM.Here we present new high resolution(～100′′)H i images of the R-C cloud,which allow us to study the
structure of the CNM on scales of0.06pc to22pc.In this paper we explore the relationship
of the R-C cloud to the ambient magnetic?eld and discuss its implications for the structure
of the CNM throughout the Milky Way.
This paper is structured as follows:in§2we discuss the data taking and reduction
strategy used.In§3we present images of the R-C cloud and in§3.1we derive optical depth
and column density maps.We present evidence of an associated magnetic?eld in§4.In
§5.1we discuss the strength of the magnetic?eld and its e?ect on the structure of the cloud. In§5.2and5.3we comment on the structure of the R-C cloud,its similarity to molecular
clouds and the implications for models for the structure of the CNM.
2.Observations and Data Analysis
The data presented here were obtained as part of an extension to the Southern Galactic
Plane Survey(SGPS;McClure-Gri?ths et al.2005).Between late2002and early2004
the SGPS was extended to cover100deg2around the Galactic Center.The SGPS Galactic
Center(GC)survey,like the main SGPS,is a survey of the21-cm continuum and H i spectral
line emission in large regions of the Galactic Plane.The GC survey covers?5?≤l≤+5?and?5?≤b≤+5?.The main goal of the SGPS GC survey is to study the structure and dynamics of H i in the inner～1kpc of the Galaxy,a topic which we will defer to a future paper.
The GC survey combines data from the Australia Telescope Compact Array(ATCA)
and the Parkes Radio Telescope for full sensitivity to angular scales from10degrees down
to the100′′resolution of the data.The Parkes data were observed and imaged as part of the
main SGPS survey and are fully described in McClure-Gri?ths et al.(2005).The ATCA
data were taken in a slightly di?erent manner than the data for the rest of the SGPS.For
completeness we describe the full ATCA GC survey parameters here.
The ATCA is an interferometer of six22m dishes situated near Narrabri,New South
Wales,Australia.ATCA data were obtained during eight observing sessions between2002
December and2004June.An additional day of make-up observations was scheduled in2004
November to?ll in gaps in the u-v coverage.The ATCA has linear feeds that receive two
orthogonal linear polarizations,X and Y,and can observe at two intermediate frequencies
(IFs)simultaneously.As in the SGPS,all data were recorded using a correlator con?guration
that records the autocorrelations,XX and Y Y,in1024channels across a4MHz bandwidth,
as well as the full polarization products,XX,Y Y,XY,and Y X,in32channels across a
128MHz bandwidth.The?rst IF was centered at1420MHz to observe the H i line and
the second was centered at1384MHz.Here we describe only the narrow-band H i data and reserve discussion of the continuum data for a future paper.
Observations were made using six east-west array con?gurations with maximum base-lines between352m and750m.Most baselines,in multiples of15m,between31m and 750m were sampled by the combination of the con?gurations EW352,EW367,750A,750B, 750C,and750D.The observing arrays and dates are given in Table1.The100deg2?eld was covered by a total of967individual pointings;948pointings were newly observed and the remaining19pointings were taken from the SGPS Phase I.All pointings were distributed on a common hexagonal pattern with a separation of19′between adjacent pointings.The ob-servations were made in snap-shot mode with60s integrations per pointing.Each pointing was observed approximately30times for a total integration time of～30min per pointing.
The primary?ux calibrator,PKS B1934-638,was observed once per day for bandpass and absolute?ux calibration,assuming a?ux at1420MHz of14.86Jy(Reynolds1994).
A secondary calibrator,PKS B1827-360,was observed approximately every45minutes for complex gain and delay calibration.Data editing and calibration were completed within the MIRIAD data reduction package using standard techniques(Sault&Killeen2004).
The967pointings were linearly combined and imaged using a standard grid-and-FFT scheme.The mosaicing process uses the joint approach,where dirty images are linearly combined and jointly deconvolved(Sault et al.1996).The joint imaging and deconvolution process improves the sensitivity to large angular scale structures,increasing the maximum scale sampled from～23′for a single pointing observation to～30′for the mosaiced image (McClure-Gri?ths et al.2005).The deconvolution uses a maximum entropy method,which is very e?ective at deconvolving large-scale emission.The maximum entropy algorithm in MIRIAD does not deconvolve the dirty beam from areas of“negative emission”,such as continuum sources observed in absorption.The Galactic center region contains many very strongly absorbed continuum sources that would not be deconvolved in standard processing. To reduce the confusing sidelobe levels observed around these sources we modeled the sources and subtracted them from the u-v data prior to imaging.Although we were not able to completely remove the sources,the resultant sidelobes were signi?cantly reduced and do not adversely a?ect the analysis of the H i cube presented here.
Finally,the deconvolved ATCA image cube was combined with the Parkes data cube to recover information on angular scales larger than～36′.This combination was performed using the MIRIAD task IMMERGE,which Fourier transforms the deconvolved ATCA and Parkes images,reweights them such that the Parkes image is given more weight for large angular scales and the ATCA image more weight for small angular scales.The weighted, Fourier transformed images are linearly combined and then inverse Fourier transformed(Sta-
nimirovi′c2002).The?nal datacube has a resolution of100′′and is sensitive to angular scales
up to the10?image size.The rms brightness temperature sensitivity in the combined cube
is～2K.The rms increases to～3K in the～1deg2immediately surrounding the Galactic
center because the broad H i line emission contributes to the ATCA system temperature.
Here we present only the part of the H i data cube pertaining to the Riegel-Crutcher cloud,
the full SGPS GC dataset will be published in a future paper.
3.Results
An H i image at an LSR velocity of4.95km s?1from the?nal,combined H i data
cube is shown in the left panel of Figure1.The Riegel-Crutcher(R-C)cloud is visible as
the large black swath that extends from upper left to the bottom right of the image.In
order to estimate the properties of the cloud itself,and to better examine its structure,we
need to separate it from the background H i emission.There are many ways of estimating
the unabsorbed H i emission,T o?,including using averages of spectra observed adjacent
to the cloud or interpolating across the absorption with a linear,parabolic or high-order
polynomial?t.Each technique has its limitations;for very extended features like the R-C
cloud,o?cloud spectra are too distant from the on-cloud positions to accurately re?ect the
unabsorbed emission.High order polynomial interpolations across the absorption pro?le
can give good estimates for T o?,but these are computationally expensive for many spectra.
Depending on the line pro?le a simple linear?t can also give a reasonable approximation to
the o?-cloud emission,with minimal computational e?ort.For simplicity we have chosen to
interpolate across the absorption with a linear?t.An example of an interpolated spectrum
and the di?erence between the absorbed and unabsorbed spectra,?T≡T on?T o?,is shown in Figure2.For each pixel in the GC cube with an absorption depth of more than8K
we searched for the edges of the absorption feature,interpolated between those edges and
replaced the intermediate channels with the interpolated spectrum.The result is a cube of
unabsorbed emission,T o?.The right panel of Fig.1shows the unabsorbed emission for the
same velocity channel as the left panel.Although the interpolation is not perfect,it has
removed the bulk of the R-C cloud.
Velocity channel images of the di?erence,?T,between the observed and the unabsorbed
cubes are shown in Fig.3.Here we show only velocity channels between3.3km s?1and7.4
km s?1,which cover the majority of the R-C cloud at these longitudes.The images have a
channel separation of0.82km s?1.The bulk of the cloud is observed in the top-left corner
of the image,from there the cloud extends to higher longitudes and latitudes,not covered
by the SGPS.In this region the cloud appears fairly smooth in structure.Extending from
the bulk of the cloud towards the lower right of the image is a wispy elongated structure. Unlike the dense top of the cloud,the tail appears to be resolved into a network of narrow ?laments,or strands,all roughly aligned.We emphasize that the edges of these?laments are real self-absorption features and are not simply places where the background emission drops away.The ensemble of?laments has a distinct curvature to it and resembles a rope of gas made up of individual strands.The individual strands appear to be mostly unresolved or in some cases marginally resolved.They have widths of between2′and5′,which,at a distance of125pc,correspond to physical widths of0.07?0.2pc.Some?laments can be traced across the majority of the image;the longest continuous?lament is7.?7,or16.9pc. Many of the?laments have aspect ratios in the range50-170:1.
3.1.Properties of the Cloud
Deriving the temperature and density of an H i cloud is non-trivial.In theory these can be derived from solutions of the radiative transfer equation.In practice,though,the radiative transfer equation cannot be solved for the complicated H i pro?les observed in the Galaxy.To derive the spin temperature,T s,and optical depth,τ,of the R-C cloud we must make some simplifying assumptions.Here we use the four-component model outlined in Gibson et al. (2000)and Kavars et al.(2003).This model assumes that all of the continuum emission,T c, originates behind the HISA cloud,but allows for both foreground and background H i with spin temperature and optical depths of T s,fg,τfg and T s,bg,τbg respectively.In this model,the radiative transfer equation can be solved for the di?erence between the observed brightness temperature on,T on,and o?the cloud,T o?.In the di?erence between on and o?cloud the direct contribution to the brightness temperature from the foreground cloud is the same and cancels out.The on-o?di?erence is given by:
?T≡T on?T o?= T s?T s,bg 1?e?τbg ?T c 1?e?τ .(1) All variables,with the exception of T c,are functions of velocity,v.We make a further assumption thatτfg andτbg are small.As in Gibson et al.(2000)we use the variable,p,to describe the fraction of the H i emission originating behind the self-absorption cloud.These assumptions allow us to solve equation(1)for the optical depth,
τ=?ln 1??T
scales is only10%of the mean continuum emission for a given latitude and not deemed important for the rough temperature analysis presented here.Included in equation(2)are the parameters T o?and p,which are not directly observed and must therefore be estimated. For T o?we use the interpolated cube described above.Although the technique of linear in-terpolation across the absorption feature can underestimate the absorption in the line wings, we?nd that the errors introduced are small when compared to?T.As our analysis does not rely heavily on accurate linewidths,this does not signi?cantly a?ect our results.To estimate p we assume that because the R-C cloud is at a distance of only125pc and lies just beyond the edge of the Local Bubble(Crutcher&Lien1984),there is very little foreground H i emission and the majority of the H i emission will be behind the cloud.We therefore assume that p is constant across the cloud and that it is equal to one,which will give a lower limit for the optical depth.We discuss the implications onτfor non-unity values of p in§3.1.2.
It is clear from equation(2)that the optical depth and spin temperature of the cloud are degenerate.Numerous authors have explored methods of constraining either T s orτ, including some e?orts applied speci?cally to the R-C.For example,Montgomery et al.(1995) estimated T s=35K by assuming that all of the measured linewidth,?v,for the narrowest absorption line can be attributed to random kinetic motions,so that T s=T k=21.6(?v)2K. This equation must be used with care,however,because it ignores all turbulent motions, which is not always an appropriate assumption.Spin temperature values estimated this way should be considered only as upper limits.This method also demands an accurate measurement of the line-width,which as Levinson&Brown(1980)caution,can be di?cult to attain for an H i self-absorption feature.
In some circumstances the line shape itself can be used to decouple T s andτ.Assuming a Gaussian optical depth of width?v,centered at v c,
τ(v)=τ0exp[?2ln4(v?v c)2/?v2],(3)
the absorption pro?le de?ned by equation(1)will?atten in the core asτ>1.In this
√
equation?v is related to the line dispersion,σ,as?v=
are also overlaid for comparison.Fitting all saturated pro?les in the GC dataset we?nd that the spin temperatures lie in the range30-65K.Because of the errors involved in this method for deriving spin temperatures these are only estimates of the https://www.doczj.com/doc/1e9464875.html,paring the range of spin temperatures that we estimate with those estimated by Montgomery et al. (1995)and Crutcher&Lien(1984)we have chosen to adopt a spin temperature of T s=40 K for the R-C cloud.It is heartening to note that this is the same value that Heeschen (1955)found in his original work on this feature.
The?t to the line pro?le also gives us an estimate for the observed line width,σobs.We assume that the measured linewidth is related to the thermal and turbulent linewidths by σobs= 8ln2σobs～3.5km s?1.For40K gas the thermal linewidth isσth～0.6km s?1,which allows us to approximate the turbulent linewidth as σturb～1.4km s?1.
3.1.1.Density and Pressure
The column density of the H i line is related to the spin temperature and optical depth by:
N HI=1.83×1018T s τ(v)dv cm?2,(4) which is valid for smallτ.Using a constant value for T s across the cloud we can solve equation (2)for the optical depth as a function of position and velocity,which may be integrated to produce a column density image for the R-C cloud.We use a constant value of T s=40K across the?eld.An image of column density in the R-C cloud is shown in Figure5.The mean column density over the entire structure is2.0±1.4×1020cm?2.The densest regions are in the body of the cloud at positive latitudes and longitudes.There we measure column densities of～4×1020cm?2,whereas the individual?laments have lower column densities of～1×1020cm?2.
These estimates for the column density and spin temperature allow us to make some order-of-magnitude estimates for the density and thermal pressure of the cloud,assuming a cloud thickness,?s.Crutcher&Lien(1984),based on stellar absorption measurements, estimate that the thickness of the R-C cloud is1-5pc.However,our images show that the individual?laments have plane-of-sky widths of less than～0.1pc.It is therefore possible that the strands are cylindrical and that the thickness of the strands is similar to the strand width,?s～0.1pc.We therefore use?s=0.1pc to estimate the H i number density,n H, and thermal pressure,P th/k=N HI T s/?s=n H T s in the individual?laments.The mean H i
density and pressure of the?laments are460cm?3and1.8×104K cm?3,respectively.The cylindrical geometry for the strands is more intuitive than a collection of edge-on ribbons. Nevertheless,the data do not exclude an edge-on ribbon scenario.If the?laments are edge-on sheets of width?s～1pc,as suggested from the lower limit of Crutcher&Lien(1984) then the mean H i density and pressure of the?laments are46cm?3and1.8×103K cm?3, respectively.For the upper left of the cloud we suggest that the smoothness is indicative of many?laments integrated along the line of sight.We therefore assume that the width of the base is1?5pc,as estimated by Crutcher&Lien(1984).Assuming?s=1?5pc,the H i density in the base is～25?130cm?3,and the pressure is(1?5)×103K cm?3.
The thermal pressure of the?laments in the R-C cloud is almost an order of magnitude larger than that expected for the CNM near the Sun,which is believed to be only P th～4000K cm?3(Wol?re et al.2003).While it is at?rst disconcerting to estimate pressures that are so far out of thermal equilibrium,these pressures are not exceptional.Jenkins&Tripp (2001)found that as much as25%of the neutral carbon bearing ISM has thermal pressures in the range P/k=103.5?4.0K cm?3and with a few percent having pressures larger than P/k=104.0K cm?3.In most areas of the ISM the thermal pressure is a small fraction of the total pressure.We can estimate the total pressure in the R-C cloud as P=σ2ρincluding both the thermal and turbulent motions,whereρis the mass density assuming10%Helium,ρ=1.4m H n H.Forσ≈1.5km s?1and an average number density of n H～460cm?4,the total pressure in the?laments is P/k～2×105K cm?3.Again the total pressure is about a factor of ten larger than total pressure(thermal plus all non-thermal components)for the general ISM in the midplane(Boulares&Cox1990).
3.1.2.Density and Pressure Caveats
It is worth taking note of some of the caveats to the density and pressure estimates given above.These estimates rely on assumptions made about T s,p,and?s.Our column density image assumes a constant spin temperature across the cloud.This is almost certainly not true,but in the absence of saturation in the H i pro?les it is not possible to solve for T s and τfor all positions.Letting T s vary randomly around the image about a mean40K with a variance of10K we found that the densities measured do not vary signi?cantly from those determined here.
The exact value of T s=40K assumed for the spin temperature has an e?ect on the densities and pressures derived.The cosmic microwave background sets an absolute mini-mum value for T s≥2.73K,which results in column densities about an order of magnitude smaller than those derived for T s=40K.Such a low spin temperature is highly unlikely in
almost all Galactic environments where the UV radiation?eld and cosmic ray heating raise
the temperature well above the CMB background.If we assume that T s=30K,which is
at the lower end of values estimated by previous authors,then the derived column densities
are a factor of～0.6smaller than for T s=40K.Values of T s>40K result in unde?ned
values ofτtowards regions where|?T|is large.
The assumed value of p can signi?cantly e?ect the derived optical depth and column
density.By assuming p=1we have minimized the optical depth for any given value of T s
and therefore minimized the densities and pressures calculated.In addition,values of p≈1
are most likely given the close proximity of the cloud.If we decrease p to an unlikely value
of0.8it has two main e?ects:?rst,the optical depth becomes unde?ned over large areas of
the map and second,the derived column densities are typically a factor of two larger than
for p=1.
Finally,the assumed cloud thickness has a large impact on the derived densities and
pressures.We have assumed a thickness for the?laments that is an order of magnitude
smaller than previous estimates by Crutcher&Lien(1984).However,Crutcher&Lien
(1984)used stellar absorption measurements at distances bracketing the cloud to estimate
its thickness.Those measurements did not have subparsec precision and they would not
have been able to exclude a thickness of less than1pc.At the other extreme,if we adopt
the Crutcher&Lien(1984)upper limit of?s=5pc for the?laments,the derived pressures
and densities will be a factor of?fty smaller than those derived for?s～0.1pc.This would
present a very unusual ribbon-like geometry for the R-C?laments,which we do not believe
is likely.
4.The Magnetic Field Structure
The?laments observed here,though curved,have virtually no wiggles.This taughtness
suggests that the gas structure may be dominated by some process other than turbulence,
such as a magnetic?eld.To explore this suggestion we have searched for the orientation of
the magnetic?eld associated with the R-C cloud.We used the Heiles(2000)compilation
of optical measurements of stellar polarization to determine the magnetic?eld direction.
From Heiles(2000)we extracted all stars at distances of less than2kpc in the region
?5?≤l≤+5?,?5?≤b≤+5?.To ensure reliable polarization angle measurements we further constrained the selection to stars with polarized intensity greater than1%of the
total intensity;56stars met the criteria.In Figure6we have overlaid polarization vectors
on the H i?T image of the R-C cloud at v=4.95km s?1.Vectors are shown at the position
of each polarized star,oriented with the polarization angle,1θp.The length of the vectors is
proportional to the measured fractional polarized intensity of the star,with a vector of5%
fractional polarization shown in the key at the bottom-left.In the regions covered by the
cloud there is a remarkable agreement between the orientation of the polarization vectors
and the direction of the cloud’s?laments.By contrast,in the area l≥?2?and b≤?3?
there is very little absorption associated with the cloud and these regions show disordered
polarization vectors.Referring only to the area covered by the cloud(l>?3?,b>?3?)the
mean polarization angle is θp =53?±11?.The polarization angle for polarization arising from polarization of background starlight is parallel to the magnetic?eld direction such that
the angle of the magnetic?eld,θB,also equals53±11?.
Stellar polarization measurements probe the magnetic?eld integrated along the line of
sight,which can lead to a superposition of structures in the observed vectors.Because we
initially included all stars out to2kpc distance it is also possible that the magnetic?eld
orientation observed is not associated with the R-C cloud,but located behind it.To test
this we examined only stars out to a distance of200pc and found that,although the sample
size is smaller,the mean polarization angle agreed with θp =53?to within the standard deviation of the full sample.This suggests that the dominant magnetic structure along this line of sight lies within200pc and the very good alignment with the R-C H i strands suggests that they are related.
5.Discussion
5.1.Magnetic Field Strength
Measurements of stellar polarization do not directly yield a measurement of the strength of the magnetic?eld.However,Chandrasekhar&Fermi(1953)suggested that the variance in an ensemble of polarization measurements can be used to estimate the strength of the ?eld.This method is often applied to measurements of starlight polarization due to dust (e.g.Andersson&Potter2006)and has been tested against theoretical MHD models by Heitsch et al.(2001)and Ostriker et al.(2001).The technique assumes that turbulence in the magnetized medium will randomize the magnetic?eld and that the stronger the regular ?eld is,the less it is disturbed by https://www.doczj.com/doc/1e9464875.html,ing the Chandrasekhar-Fermi(C-F)method, as modi?ed by Heitsch et al.(2001),the strength of the magnetic?eld in the plane of the
sky can be estimated as:
B 2=ξ4πρσ2v
ergs cm?3,(6)
?s
where?v is in km s?1and?s is in pc.Considering just the?laments of the R-C cloud, where N H～1×1020cm?2,?v～3.5km s?1,and?s≈0.07pc if the?laments are cylinders, then the kinetic energy density is K=3.7×10?11ergs cm?3.If the?laments are edge-on ribbons instead of cylinders then the kinetic energy density will be smaller.
If we approximate the?laments as cylinders of r=?s/2and length L,then the total gravitational energy is given by W=?GM2/L(Fiege&Pudritz2000)and the gravitational energy density is:
G=Gπ(1.4m H n H r)2,(7) For the R-C?laments,the gravitational energy density is G～3×10?15ergs cm?3.The
gravitational energy density is very small compared to the kinetic energy density;these ?laments are clearly not self-gravitating.
Finally,the magnetic energy density is M=|B tot|2/8π,where B tot≥B meas.Given negligible gravitational energy density,for the magnetic?eld to dominate the structure observed in the R-C cloud,M>K.For K～3.7×10?11ergs cm?3the magnetic?eld strength must be B tot>30μG.The agreement between the magnetic?eld strength derived assuming magnetic dominance and with the C-F method is surprisingly good.One can use this result and Eq.5to solve forξfor the R-C cloud.A?eld strength of>30μG implies that the correction factor,ξ,for this cloud should be>0.12.
To better understand the magnetic?eld of the R-C cloud we would also require mea-surements of the line-of-sight magnetic?eld strength.Most measurements of magnetic?elds in the CNM have been made using Zeeman splitting(e.g Heiles&Troland2005),which probes the line-of-sight component of the?eld.Heiles&Troland(2005)?nd a median CNM magnetic?eld strength of6.0±1.8μG over a wide range of Galactic environments.This is considerably lower than the values estimated here for the R-C cloud.It is important to note,however,that the density of the R-C cloud is larger than typical CNM values.In fact, the magnetic?eld strength estimated is more consistent with values obtained for molecular clouds with densities similar to that of the R-C cloud(Crutcher1999).However,for these measurements it is usually assumed that gravitational contraction compresses the magnetic ?eld lines leading to an increase in density and magnetic?eld strength.There is no evidence for such action in the R-C cloud and it is therefore curious that it should exhibit such a high magnetic?eld strength.
https://www.doczj.com/doc/1e9464875.html,ments on the Structure of the CNM
The structure of the cold neutral medium(CNM)is very di?cult to study.For many years we have harbored the notion that the CNM was distributed in isotropic clouds as described in the McKee&Ostriker(1977)paradigm.However,there is a fair amount of evidence against this model.For example,high resolution H i absorption measurements towards pulsars and radio galaxies?nd very small-scale variations in the H i that seem to require unreasonably high thermal pressures if we assume they are spherical.Heiles(1997) invoked geometry to explain this“tiny scale atomic structure”(TSAS),suggesting instead that these measurements probe cold gas in thin sheets viewed edge-on or?laments viewed end-on.Although the sheet or?lament description is appealing because of its resolution of the overpressure problem,it has not been readily adopted,owing largely to the lack of ob-servational evidence for counterparts aligned perpendicular to the line of sight.These sheets
or?laments are predicted to have very low column densities,rendering them unobservable (Heiles1997).There is evidence that on larger scales the CNM is indeed in large-scale?la-ments of sheets.In the few examples where we can image large areas of the CNM through H i self-absorption,such as in the CGPS and SGPS(Gibson et al.2005;Kavars et al.2005),the CNM seems extended,with complicated structure that is far from isotropic.H i absorption measurements towards closely separated continuum sources support this view with similar absorption components that suggest extended CNM clouds with aspect ratios～10?200 (Heiles&Troland2003).With our images we?nd that the cold medium of the R-C does not resemble the spherical clouds of McKee&Ostriker(1977)but instead is structurally much closer to the Heiles(1997)description of?laments.Our?laments di?er from those proposed by Heiles(1997)in that they are viewed side-on,rather than end-on.Although the size scales represented by the R-C cloud are more than two orders of magnitude larger than those observed in TSAS,the R-C cloud presents evidence that the CNM on small scales is structured in?laments with extreme aspect ratios.
https://www.doczj.com/doc/1e9464875.html,parison with Molecular Clouds
As much as60%of the H i self-absorption features observed in the inner Galactic plane have some association with molecular gas as detected by12CO emission(Kavars et al.2005). Comparing the H i data with data from the low resolution(30′)12CO survey(Dame et al. 1987),there is some indication for associated CO emission at high latitudes around v≈3.5 km s?1.Without CO data of comparable resolution to the H i it is di?cult to make a clear association between the H i self-absorption?laments and CO emission.Although CO emission in the dense base of the R-C cloud seems reasonable,CO emission in the?laments would be surprising.The?laments’column densities of～1×1020cm?2should account for only～0.05mag of visual extinction,which is below the extinction limit generally required to shield CO from photo-dissociation(van Dishoeck&Black1988).
Despite the lack of clear molecular emission in the?laments it may be informative to compare the?lamentary structure of the R-C cloud with that seen in molecular clouds. Kavars et al.(2005)suggest that gas probed by H i self-absorption may?ll the evolutionary gap between di?use atomic clouds and molecular clouds.The density of the R-C cloud ?laments,n～460cm?3is much higher than most H i self-absorption features(Kavars et al.2005)and indeed most of the CNM(Heiles&Troland2003),it is instead closer to the low end of molecular cloud densities(Crutcher1999).Morphologically,the R-C cloud is reminiscent of the structure observed in some molecular clouds.Molecular clouds have long been observed to have elongated?lamentary structure similar to that observed in the
R-C cloud.Good examples of?lamentary molecular clouds are the Taurus,ρOphiuchus and Orion molecular clouds,which show long molecular?laments with dense clumps along their lengths(e.g.Mizuno et al.1995;Falgarone et al.2001).Although it is not clear how ?lamentary structure develops in molecular clouds,it is expected that magnetic?elds play an important role in establishing and maintaining their structure.
Far-infrared polarization observations of?lamentary molecular clouds show that very often the polarization vectors are oriented either along or perpendicular to the?laments (Matthews&Wilson2000).This bimodal distribution has often been attributed to helical magnetic?elds that wrap around the?laments(Carlqvist&Kristen1997;Fiege&Pudritz 2000).However,reliably inferring the three dimensional magnetic?eld structure from plane-of-sky dust polarization measurements is di?cult.Some of the most promising evidence for helical magnetic?eld structure has come from Zeeman measurements of Orion A(Robishaw &Heiles2005),which show the?eld reversing direction on opposite sides of the?lament.
A fundamental di?erence between?lamentary molecular clouds and the R-C cold H i ?laments is that molecular clouds are in general self-gravitating.Depending on the?eld geometry the magnetic?eld in molecular clouds can provide crucial support against gravi-tational collapse.For example,for?elds aligned along the direction of elongation(poloidal ?elds)the magnetic?eld provides an outwards pressure to counter the gravitational con-traction.For helical?elds the situation is more complex with the net pressure e?ect at the surface of the cloud depending on the relative strengths of the poloidal and azimuthal com-ponents.For helical?elds where the azimuthal component dominates the magnetic pressure acts inwards.
For the R-C cloud the true con?guration of the magnetic?eld is crucial to de?ning the cloud life-time.It is also particularly di?cult to distinguish the?eld con?guration within the cloud from the con?guration of the ambient?eld from the stellar polarization alone.If the?eld within the?laments is poloidal or helical with a dominant poloidal component,as the observed polarization vectors suggest,then the magnetic?eld has the e?ect of increasing the total pressure.The over-pressurized?laments should be short-lived with radial crossing times on the order of4×104yr.If,on the other hand,the?eld within the?laments is actually helical and has places where the azimuthal?eld dominates,then the magnetic pressure may stabilize against the thermal pressure and could even lead to collapse and fragmentation of the?laments.Unfortunately it is impossible to infer the true internal magnetic?eld con?guration from the starlight polarization data of these multiple superimposed?laments. Zeeman measurements of the line-of-sight magnetic?eld component are needed to understand the dynamical future of the R-C cloud.
6.Conclusions
We have presented new high resolution H i self-absorption images of part of the Riegel-Crutcher(R-C)cold cloud at a distance of125pc in the direction of the Galactic center. These images,which are part of the SGPS Galactic Center survey,cover the area?5?≤l≤5?,?5?≤b≤5?with an angular resolution of100arcseconds.The data reveal extraordinary
?lamentary structure within the R-C cloud.The cloud seems to be composed of a network of aligned narrow?laments that merge into a smooth mass at the upper left of the cloud. The?laments are very elongated,with the most extreme example only0.07pc wide and over 16pc https://www.doczj.com/doc/1e9464875.html,ing saturated absorption pro?les in the cloud we estimate a spin temperature for the cloud of T s～40K,which is similar to values previously estimated by Crutcher& Riegel(1974)and Montgomery et al.(1995).Adopting a spin temperature of40K for the entire cloud we created images of the optical depth and column density of the cloud,?nding an average column density of～2×1020cm?2.If the individual?laments of the cloud are approximated as cylinders,then their average thermal pressure is～2×104K cm?3.
From measurements of the polarization of starlight from Heiles(2000)we have shown that the?laments in the R-C cloud are aligned with the magnetic?eld of the https://www.doczj.com/doc/1e9464875.html,ing the Chandrasekhar-Fermi method we have roughly estimated the magnetic?eld strength to be～60μG.By comparing ratios of gravitational,kinetic and magnetic energy densities we show that the?laments are not self-gravitating.We suggest that the excellent alignment between the?laments and the magnetic?eld,as well as the straightness of the?laments,is evidence that the magnetic?eld dominates over thermal and turbulent motions within the cloud.For the magnetic energy density to exceed the kinetic energy density the magnetic ?eld must be>30μG.Given the uncertainties associated with the Chandrasekhar-Fermi method the two?eld strengths are fully consistent.
Directly imaging the structure of the CNM is always di?cult.The R-C cloud,because it is in front of the bright,high column density H i background towards the Galactic center, provides us with a unique opportunity to directly image the CNM.In this case the CNM appears highly?lamentary and most closely resembles the high aspect ratio?laments sug-gested by Heiles(1997)to explain Tiny Scale Atomic Structure.There is no reason to believe that the structure of the R-C cloud is unique,it may in fact be typical for the CNM.We point out that there are morphological similarities between the R-C cloud and?lamentary molecular clouds,which are also characterized by strong magnetic?elds.If gas traced by H i self-absorption is either a precursor to molecular gas or formed from dissociation of molecular clouds the morphological similarity is not surprising.
The Parkes Radio Telescope and the Australia Telescope Compact Array are part of
the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.MH acknowledges support from the National Radio Astronomy Observatory(NRAO),which is operated by Associated Universities Inc., under cooperative agreement with the National Science Foundation.The authors thank an anonymous referee for insightful and interesting questions and suggestions.
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Table1.SGPS Galactic Center ATCA Observations
Dates Array Con?guration
a Make-up session.
如何写先进个人事迹 篇一：如何写先进事迹材料 如何写先进事迹材料 一般有两种情况：一是先进个人，如先进工作者、优秀党员、劳动模范等；一是先进集体或先进单位，如先进党支部、先进车间或科室，抗洪抢险先进集体等。无论是先进个人还是先进集体，他们的先进事迹，内容各不相同，因此要整理材料，不可能固定一个模式。一般来说，可大体从以下方面进行整理。 (1)要拟定恰当的标题。先进事迹材料的标题，有两部分内容必不可少，一是要写明先进个人姓名和先进集体的名称，使人一眼便看出是哪个人或哪个集体、哪个单位的先进事迹。二是要概括标明先进事迹的主要内容或材料的用途。例如《王鬃同志端正党风的先进事迹》、《关于评选张鬃同志为全国新长征突击手的材料》、《关于评选鬃处党支部为省直机关先进党支部的材料》等。 (2)正文。正文的开头，要写明先进个人的简要情况，包括：姓名、性别、年龄、工作单位、职务、是否党团员等。此外，还要写明有关单位准备授予他(她)什么荣誉称号，或给予哪种形式的奖励。对先进集体、先进单位，要根据其先进事迹的主要内容，寥寥数语即应写明，不须用更多的文字。 然后，要写先进人物或先进集体的主要事迹。这部分内容是全篇材料
的主体，要下功夫写好，关键是要写得既具体，又不繁琐；既概括，又不抽象；既生动形象，又很实在。总之，就是要写得很有说服力，让人一看便可得出够得上先进的结论。比如，写一位端正党风先进人物的事迹材料，就应当着重写这位同志在发扬党的优良传统和作风方面都有哪些突出的先进事迹，在同不正之风作斗争中有哪些突出的表现。又如，写一位搞改革的先进人物的事迹材料，就应当着力写这位同志是从哪些方面进行改革的，已经取得了哪些突出的成果，特别是改革前后的．经济效益或社会效益都有了哪些明显的变化。在写这些先进事迹时，无论是先进个人还是先进集体的，都应选取那些具有代表性的具体事实来说明。必要时还可运用一些数字，以增强先进事迹材料的说服力。 为了使先进事迹的内容眉目清晰、更加条理化，在文字表述上还可分成若干自然段来写，特别是对那些涉及较多方面的先进事迹材料，采取这种写法尤为必要。如果将各方面内容材料都混在一起，是不易写明的。在分段写时，最好在每段之前根据内容标出小标题，或以明确的观点加以概括，使标题或观点与内容浑然一体。 最后，是先进事迹材料的署名。一般说，整理先进个人和先进集体的材料，都是以本级组织或上级组织的名义；是代表组织意见的。因此，材料整理完后，应经有关领导同志审定，以相应一级组织正式署名上报。这类材料不宜以个人名义署名。 写作典型经验材料-般包括以下几部分： (1)标题。有多种写法，通常是把典型经验高度集中地概括出来，一
How to manage time Time treats everyone fairly that we all have 24 hours per day. Some of us are capable to make good use of time while some find it hard to do so. Knowing how to manage them is essential in our life. Take myself as an example. When I was still a senior high student, I was fully occupied with my studies. Therefore, I hardly had spare time to have fun or develop my hobbies. But things were changed after I entered university. I got more free time than ever before. But ironically, I found it difficult to adjust this kind of brand-new school life and there was no such thing called time management on my mind. It was not until the second year that I realized I had wasted my whole year doing nothing. I could have taken up a Spanish course. I could have read ten books about the stories of successful people. I could have applied for a part-time job to earn some working experiences. B ut I didn’t spend my time on any of them. I felt guilty whenever I looked back to the moments that I just sat around doing nothing. It’s said that better late than never. At least I had the consciousness that I should stop wasting my time. Making up my mind is the first step for me to learn to manage my time. Next, I wrote a timetable, setting some targets that I had to finish each day. For instance, on Monday, I must read two pieces of news and review all the lessons that I have learnt on that day. By the way, the daily plan that I made was flexible. If there’s something unexpected that I had to finish first, I would reduce the time for resting or delay my target to the next day. Also, I would try to achieve those targets ahead of time that I planed so that I could reserve some more time to relax or do something out of my plan. At the beginning, it’s kind of difficult to s tick to the plan. But as time went by, having a plan for time in advance became a part of my life. At the same time, I gradually became a well-organized person. Now I’ve grasped the time management skill and I’m able to use my time efficiently.
英语演讲稿：未来的工作 这篇《英语演讲稿范文：未来的工作》，是特地，希望对大家有所帮助！ 热门演讲推荐：竞聘演讲稿 | 国旗下演讲稿 | 英语演讲稿 | 师德师风演讲稿 | 年会主持词 | 领导致辞 everybody good afternoon:. first of all thank the teacher gave me a story in my own future ideal job. everyone has a dream job. my dream is to bee a boss, own a pany. in order to achieve my dreams, i need to find a good job, to accumulate some experience and wealth, it is the necessary things of course, in the school good achievement and rich knowledge is also very important. good achievement and rich experience can let me work to make the right choice, have more opportunities and achievements. at the same time, munication is very important, because it determines whether my pany has a good future development. so i need to exercise their municative ability. i need to use all of the free time to learn
世界经典哲学类书籍 哲学，是理论化、系统化的世界观，是自然知识、社会知识、思维知识的概括和总结,是世界观和方法论的统一。是社会意识的具体存在和表现形式，是以追求世界的本源、本质、共性或绝对、终极的形而上者为形式，以确立哲学世界观和方法论为内容的社会科学。 《性心理学》 《作为意志和表象的世界》 《理想国》 《西方哲学史》 《自然哲学的数学原理》 《权力意志》 《新工具》 《纯粹理性批判》《文明论概略》 《劝学篇》 《伦理学》 《耶稣传》 《时间简史》 《逻辑哲学论》 《精神现象学》 《物性论》 《感觉的分析》 《精神分析引论》《基督何许人也——基督抹煞论》 《科学的社会功能》《人有人的用处》《科学史》 《人类理智新论》《逻辑学》 《哲学研究》 《新系统及其说明》《道德情操论》 《实践理性批判》《美学》 《判断力批判》 《基督教的本质》《薄伽梵歌》 《伦理学中的形式主义与质料的价值伦理学》《物种起源》 《物理学》《人类的由来》 《人性论》 《人是机器》 《法哲学原理》 《狄德罗哲学选集》 《野性的思维》 《哲学史教程》 《科学与近代世界》 《人类的知识》 《精神分析引论新编》 《自然宗教对话录》 《基督教并不神秘》 《科学中华而不实的 作风》 《一年有半，续一年有 半》 《时间与自由意志》 《哲学辞典》 《历史理性批判文集》 《苏鲁支语录》 《文化科学和自然科 学》 《十六、十七世纪科 学、技术和哲学史》 《科学哲学的兴起》 《灵魂论及其他》 《斯宾诺莎书信集》 《实验心理学史》 《最后的沉思》 《纯粹现象学通论》 《近代心理学历史导 引》 《佛教逻辑》 《神圣人生论》 《逻辑与知识》 《论原因、本原与太 一》 《形而上学导论》 《诗学》 《路标》 《心的概念》 《计算机与人脑》 《十七世纪英格兰的 科学、技术与社会》 《卡布斯教诲录》 《薄伽梵歌论》 《尼各马可伦理学》 《论老年论友谊论责 任》 《实用主义》 《我的哲学的发展》 《拓扑心理学原理》 《在通向语言的途中》 《科学社会学》 《埃克哈特大师文集》 《逻辑大全》 《简论上帝、人及其心 灵健康》 《宗教的本质》 《论灵魂》 《科学的价值》 《内时间意识现象学》 《艺术即经验》 《宗教与科学》 《感觉与可感物》 《行为的结构》 《真理与方法》 《阿维斯塔》 《善的研究》 《人类知识原理》 《伦理学体系》 《科学与方法》 《第一哲学（上下卷）》 《物理学理论的目的 与结构》 《思维方式》 《发生认识论原理》 《爱因斯坦文集》 《伦理学的两个基本问题》 《数理哲学导论 《耶稣传（第一、二卷）》 《美学史》 《原始思维》 《面向思的事情》 《普通认识论》 《莱布尼茨与克拉克论战 书信集》 《对莱布尼茨哲学的批评 性解释》 《物理学和哲学》 《尼采（上下卷）》 《思想录》 《道德原则研究》 《自我的超越性》 《实验医学研究导论》 《巴曼尼得斯篇》 《人类理解论》 《笛卡尔哲学原理》 《人生的亲证》 《认识与谬误》 《哲学史讲演录》 《圣教论》 《哲学作为严格的科学》 《人类知识起源论》 《回忆苏格拉底》 《心的分析》 《任何一种能够作为科学 出现的未来形而上学导论》 《科学与假设》 《宗教经验之种种》 《声音与现象》 《苏格拉底的申辩》 《论个人在历史上的作用 问题》 《论有学识的无知》 《保卫马克思》 《艺术的起源》
小学生个人读书事迹简介怎么写800字 书,是人类进步的阶梯,苏联作家高尔基的一句话道出了书的重要。书可谓是众多名人的“宠儿”。历来,名人说出关于书的名言数不胜数。今天小编在这给大家整理了小学生个人读书事迹,接下来随着小编一起来看看吧! 小学生个人读书事迹1 “万般皆下品,惟有读书高”、“书中自有颜如玉,书中自有黄金屋”,古往今来,读书的好处为人们所重视,有人“学而优则仕”,有人“满腹经纶”走上“传道授业解惑也”的道路……但是,从长远的角度看,笔者认为读书的好处在于增加了我们做事的成功率,改善了生活的质量。 三国时期的大将吕蒙,行伍出身,不重视文化的学习,行文时,常常要他人捉刀。经过主君孙权的劝导,吕蒙懂得了读书的重要性,从此手不释卷,成为了一代儒将,连东吴的智囊鲁肃都对他“刮目相待”。后来的事实证明,荆州之战的胜利,擒获“武圣”关羽,离不开吕蒙的“运筹帷幄,决胜千里”,而他的韬略离不开平时的读书。由此可见,一个人行事的成功率高低,与他的对读书,对知识的重视程度是密切相关的。 的物理学家牛顿曾近说过,“如果我比别人看得更远,那是因为我站在巨人的肩上”,鲜花和掌声面前,一代伟人没有迷失方向,自始至终对读书保持着热枕。牛顿的话语告诉我们,渊博的知识能让我们站在更高、更理性的角度来看问题,从而少犯错误,少走弯路。
读书的好处是显而易见的,但是,在社会发展日新月异的今天,依然不乏对读书,对知识缺乏认知的人,《今日说法》中我们反复看到农民工没有和用人单位签订劳动合同,最终讨薪无果;屠户不知道往牛肉里掺“巴西疯牛肉”是犯法的;某父母坚持“棍棒底下出孝子”,结果伤害了孩子的身心,也将自己送进了班房……对书本,对知识的零解读让他们付出了惨痛的代价,当他们奔波在讨薪的路上,当他们面对高墙电网时,幸福,从何谈起?高质量的生活,从何谈起? 读书,让我们体会到“锄禾日当午,汗滴禾下土”的艰辛;读书,让我们感知到“四海无闲田,农夫犹饿死”的无奈;读书,让我们感悟到“为报倾城随太守,西北望射天狼”的豪情壮志。 读书的好处在于提高了生活的质量,它填补了我们人生中的空白,让我们不至于在大好的年华里无所事事,从书本中,我们学会提炼出有用的信息,汲取成长所需的营养。所以,我们要认真读书,充分认识到读书对改善生活的重要意义,只有这样,才是一种负责任的生活态度。 小学生个人读书事迹2 所谓读一本好书就是交一个良师益友,但我认为读一本好书就是一次大冒险,大探究。一次体会书的过程,真的很有意思,咯咯的笑声,总是从书香里散发;沉思的目光也总是从书本里透露。是书给了我启示,是书填补了我无聊的夜空,也是书带我遨游整个古今中外。所以人活着就不能没有书,只要爱书你就是一个爱生活的人,只要爱书你就是一个大写的人,只要爱书你就是一个懂得珍惜与否的人。可真所谓
关于坚持的英语演讲稿 Results are not important, but they can persist for many years as a commemoration of. Many years ago, as a result of habits and overeating formed one of obesity, as well as indicators of overall physical disorders, so that affects my work and life. In friends to encourage and supervise, the participated in the team Now considered to have been more than three years, neither the fine rain, regardless of winter heat, a day out with 5:00 time. The beginning, have been discouraged, suffering, and disappointment, but in the end of the urging of friends, to re-get up, stand on the playground. 成绩并不重要，但可以作为坚持多年晨跑的一个纪念。多年前，由于庸懒习惯和暴饮暴食，形成了一身的肥胖，以及体检指标的全盘失常，以致于影响到了我的工作和生活。在好友的鼓励和督促下，参加了晨跑队伍。现在算来，已经三年多了，无论天晴下雨，不管寒冬酷暑，每天五点准时起来出门晨跑。开始时，也曾气馁过、痛苦过、失望过，但最后都在好友们的催促下，重新爬起来，站到了操场上。 In fact, I did not build big, nor strong muscles, not a sport-born people. Over the past few years to adhere to it, because I have a team behind, the strength of a strongteam here, very grateful to our team, for a long time, we encourage each other, and with sweat, enjoying common health happy. For example, Friends of the several run in order to maintain order and unable to attend the 10，000 meters race, and they are always concerned about the brothers and promptly inform the place and time, gives us confidence and courage. At the same time, also came on their own inner desire and pursuit for a good health, who wrote many of their own log in order to refuel for their own, and inspiring. 其实我没有高大身材，也没健壮肌肉，天生不属于运动型的人。几年来能够坚持下来，因为我的背后有一个团队，有着强大团队的力量，在这里，非常感谢我们的晨跑队，长期以来，我们相互鼓励着，一起流汗，共同享受着健康带来的快
1.How to build a business that lasts100years 0:11Imagine that you are a product designer.And you've designed a product,a new type of product,called the human immune system.You're pitching this product to a skeptical,strictly no-nonsense manager.Let's call him Bob.I think we all know at least one Bob,right?How would that go? 0:34Bob,I've got this incredible idea for a completely new type of personal health product.It's called the human immune system.I can see from your face that you're having some problems with this.Don't worry.I know it's very complicated.I don't want to take you through the gory details,I just want to tell you about some of the amazing features of this product.First of all,it cleverly uses redundancy by having millions of copies of each component--leukocytes,white blood cells--before they're actually needed,to create a massive buffer against the unexpected.And it cleverly leverages diversity by having not just leukocytes but B cells,T cells,natural killer cells,antibodies.The components don't really matter.The point is that together,this diversity of different approaches can cope with more or less anything that evolution has been able to throw up.And the design is completely modular.You have the surface barrier of the human skin,you have the very rapidly reacting innate immune system and then you have the highly targeted adaptive immune system.The point is,that if one system fails,another can take over,creating a virtually foolproof system. 1:54I can see I'm losing you,Bob,but stay with me,because here is the really killer feature.The product is completely adaptive.It's able to actually develop targeted antibodies to threats that it's never even met before.It actually also does this with incredible prudence,detecting and reacting to every tiny threat,and furthermore, remembering every previous threat,in case they are ever encountered again.What I'm pitching you today is actually not a stand-alone product.The product is embedded in the larger system of the human body,and it works in complete harmony with that system,to create this unprecedented level of biological protection.So Bob,just tell me honestly,what do you think of my product? 2:47And Bob may say something like,I sincerely appreciate the effort and passion that have gone into your presentation,blah blah blah-- 2:56(Laughter) 2:58But honestly,it's total nonsense.You seem to be saying that the key selling points of your product are that it is inefficient and complex.Didn't they teach you 80-20?And furthermore,you're saying that this product is siloed.It overreacts, makes things up as it goes along and is actually designed for somebody else's benefit. I'm sorry to break it to you,but I don't think this one is a winner.
关于工作的优秀英语演讲稿 Different people have various ambitions. Some want to be engineers or doctors in the future. Some want to be scientists or businessmen. Still some wish to be teachers or lawers when they grow up in the days to come. Unlike other people, I prefer to be a farmer. However, it is not easy to be a farmer for Iwill be looked upon by others. Anyway,what I am trying to do is to make great contributions to agriculture. It is well known that farming is the basic of the country. Above all, farming is not only a challenge but also a good opportunity for the young. We can also make a big profit by growing vegetables and food in a scientific way. Besides we can apply what we have learned in school to farming. Thus our countryside will become more and more properous. I believe that any man with knowledge can do whatever they can so long as this job can meet his or her interest. All the working position can provide him with a good chance to become a talent. 1 ————来源网络整理，仅供供参考
个人先进事迹简介 01 在思想政治方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.利用课余时间和党课机会认真学习政治理论,积极向党组织靠拢. 在学习上,xxxx同学认为只有把学习成绩确实提高才能为将来的实践打下扎实的基础,成为社会有用人才.学习努力、成绩优良. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意识和良好的心理素质和从容、坦诚、乐观、快乐的生活态度,乐于帮助身边的同学,受到师生的好评. 02 xxx同学认真学习政治理论,积极上进,在校期间获得原院级三好生,和校级三好生,优秀团员称号,并获得三等奖学金. 在学习上遇到不理解的地方也常常向老师请教,还勇于向老师提出质疑.在完成自己学业的同时,能主动帮助其他同学解决学习上的难题,和其他同学共同探讨,共同进步. 在社会实践方面,xxxx同学参与了中国儿童文学精品“悦”读书系,插画绘制工作,xxxx同学在班中担任宣传委员,工作积极主动,认真负责,有较强的组织能力.能够在老师、班主任的指导下独立完成学院、班级布置的各项工作. 03 xxx同学在政治思想方面积极进取,严格要求自己.在学习方面刻苦努力,不断钻研,学习成绩优异,连续两年荣获国家励志奖学金；作
为一名学生干部,她总是充满激情的迎接并完成各项工作,荣获优秀团干部称号.在社会实践和志愿者活动中起到模范带头作用. 04 xxxx同学在思想方面,积极要求进步,为人诚实,尊敬师长.严格 要求自己.在大一期间就积极参加了党课初、高级班的学习,拥护中国共产党的领导,并积极向党组织靠拢. 在工作上,作为班中的学习委员,对待工作兢兢业业、尽职尽责 的完成班集体的各项工作任务.并在班级和系里能够起骨干带头作用.热心为同学服务,工作责任心强. 在学习上,学习目的明确、态度端正、刻苦努力,连续两学年在 班级的综合测评排名中获得第1.并荣获院级二等奖学金、三好生、优秀班干部、优秀团员等奖项. 在社会实践方面,积极参加学校和班级组织的各项政治活动,并 在志愿者活动中起到模范带头作用.积极锻炼身体.能够处理好学习与工作的关系,乐于助人,团结班中每一位同学,谦虚好学,受到师生的好评. 05 在思想方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.作为一名共产党员时刻起到积极的带头作用,利用课余时间和党课机会认真学习政治理论. 在工作上,作为班中的团支部书记,xxxx同学积极策划组织各类 团活动,具有良好的组织能力. 在学习上,xxxx同学学习努力、成绩优良、并热心帮助在学习上有困难的同学,连续两年获得二等奖学金. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意 识和良好的心理素质.
尊敬的领导，老师，亲爱的同学们， 大家好！我是5班的梁浩东。今天早上我坐车来学校的路上，我仔细观察了路上形形色色的人，有开着小车衣着精致的叔叔阿姨，有市场带着倦容的卖各种早点的阿姨，还有偶尔穿梭于人群中衣衫褴褛的乞丐。于是我问自己，十几年后我会成为怎样的自己，想成为社会成功人士还是碌碌无为的人呢，答案肯定是前者。那么十几年后我怎样才能如愿以偿呢，成为一个受人尊重，有价值的人呢？正如我今天演讲的题目是：自主管理。 大家都知道爱玩是我们孩子的天性，学习也是我们的责任和义务。要怎样处理好这些矛盾，提高自主管理呢？ 首先，我们要有小主人翁思想，自己做自己的主人，要认识到我们学习，生活这一切都是我们自己走自己的人生路，并不是为了报答父母，更不是为了敷衍老师。 我认为自主管理又可以理解为自我管理，在学习和生活中无处不在，比如通过老师，小组长来管理约束行为和同学们对自身行为的管理都属于自我管理。比如我们到一个旅游景点，看到一块大石头，有的同学特别兴奋，会想在上面刻上：某某某到此一游话。这时你就需要自我管理，你需要提醒自己，这样做会破坏景点，而且是一种素质低下的表现。你设想一下，如果别人家小孩去你家墙上乱涂乱画，你是何种感受。同样我们把自主管理放到学习上，在我们想偷懒，想逃避，想放弃的时候，我们可以通过自主管理来避免这些，通过他人或者自己的力量来完成。例如我会制定作息时间计划表，里面包括学习，运动，玩耍等内容的完成时间。那些学校学习尖子，他们学习好是智商高于我们吗，其实不然，在我所了解的哪些优秀的学霸传授经验里，就提到要能够自我管理，规范好学习时间的分分秒秒，只有辛勤的付出，才能取得优异成绩。 在现实生活中，无数成功人士告诉我们自主管理的重要性。十几年后我想成为一位优秀的，为国家多做贡献的人。亲爱的同学们，你们们？让我们从现在开始重视和执行自主管理，十几年后成为那个你想成为的人。 谢谢大家！
关于工作的英语演讲稿 【篇一：关于工作的英语演讲稿】 关于工作的英语演讲稿 different people have various ambitions. some want to be engineers or doctors in the future. some want to be scientists or businessmen. still some wish to be teachers or lawers when they grow up in the days to come. unlike other people, i prefer to be a farmer. however, it is not easy to be a farmer for iwill be looked upon by others. anyway,what i am trying to do is to make great contributions to agriculture. it is well known that farming is the basic of the country. above all, farming is not only a challenge but also a good opportunity for the young. we can also make a big profit by growing vegetables and food in a scientific way. besides we can apply what we have learned in school to farming. thus our countryside will become more and more properous. i believe that any man with knowledge can do whatever they can so long as this job can meet his or her interest. all the working position can provide him with a good chance to become a talent. 【篇二：关于责任感的英语演讲稿】 im grateful that ive been given this opportunity to stand here as a spokesman. facing all of you on the stage, i have the exciting feeling of participating in this speech competition. the topic today is what we cannot afford to lose. if you ask me this question, i must tell you that i think the answer is a word---- responsibility. in my elementary years, there was a little girl in the class who worked very hard, however she could never do satisfactorily in her lessons. the teacher asked me to help her, and it was obvious that she expected a lot from me. but as a young boy, i was so restless and thoughtless, i always tried to get more time to play and enjoy myself. so she was always slighted over by me. one day before the final exam, she came up to me and said, could you please explain this to me? i can not understand it. i
第五章老年社会工作 第一节老年社会工作概述 第二节老年社会工作的主要内容 第三节老年社会工作的主要方法 第一节老年社会工作概述 一、老年人与老年期 （一）年龄界定 生理年龄：生理指标与功能确定 心理年龄：心理活动程度确定 社会年龄：与他人交往的角色确定 （二）老年期的划分 低龄老年人：60-69岁 中龄老年人：70-79 高龄老年人：80岁以上 （三）划分的意义 1.三种年龄：不能仅凭日历年龄判断服务需求，而要关注不同个体在生理、心理与社会方面的差异。 2.三个时期：关注老年同期群的共性需要。 二、老年期的特点 （一）生理变化 1.生理变化的特点：九大生理系统老化 2.对开展老年社会工作的影响 （1）要特别关注老年人的身体健康状况； （2）处理好隐私的健康问题，如大小便； （3）帮助机构和家庭策划环境的调整。 （二）心理变化 1.智力、人格、记忆力的变化 智力：结晶智力强，但处理问题速度下降 人格：总结自己生命的意义 记忆力：记忆速度下降，动机决定是否学习 2.对开展老年社工的影响 （1）提供机会但尊重选择 （2）所有事放慢节奏 （3）关注身体健康对心理功能的重要性 （三）社会生活方面的变化 1.对老年社会生活变化的理论解释 （1）角色理论：丧失象征中年的社会角色 （2）活动理论：生活满足感与活动有积极联系 （3）撤离理论：接受减少与社会的交往 （4）延续理论：不能割裂看待老年阶段 （5）社会建构理论：老年是一个独特的个人过程 （6）现代化理论：现代化使老年人地位下降
2.理论在社会工作中的应用 （1）注意角色转变的重大生活事件 （2）注意老年个体的差异性，尊重其对生活意义的不同理解 （3）注意社会隔离可能对老年人造成的伤害 （4）改变总有可能 （5）关注社会变迁对老年人的影响，推动社会政策的调整 三、老年人的需要及问题 （一）老年人的需要 1.健康维护 2.经济保障 3.就业休闲 4.社会参与 5.婚姻家庭 6.居家安全 7.后事安排 8.一条龙照顾 （二）老年人的问题 1.慢性病问题与医疗问题 2.家庭照顾问题 3.宜居环境问题 4.代际隔阂问题 5.社会隔离问题 四、老年社会工作 （一）老年社会工作的对象 1.老年人自身：空巢、残疾、高龄老人，也包括健康老人 2.老年人周围的人：家庭成员、亲属、朋友、邻居等 3.宏观系统：单位与服务组织 （二）老年社会工作的目的 根本目标：老有所养、老有所医、老有所教、老有所学、老有所为、老有所乐 （三）老年社会工作的作用 1.个体层面：维持日常生活、获得社会支持 2.宏观层面：参与制定有关老年人的服务方案与政策 五、老年社会工作的特点 （一）老年歧视等社会价值观会影响社会工作者的态度与行为 （二）反移情是社会工作者的重要课题 （三）社会工作者要善于运用督导机制 （四）需要多学科合作 第二节老年社会工作的主要内容 一、身体健康方面的服务 二、认知与情绪问题的处理 三、精神问题的解决 四、社会支持网络的建立 五、老年人特殊问题的处理 一、身体健康方面的服务
Dear teacher and colleagues: my topic is on “spare time”. It is a huge blessing that we can work 996. Jack Ma said at an Ali's internal communication activity, That means we should work at 9am to 9pm, 6 days a week .I question the entire premise of this piece. but I'm always interested in hearing what successful and especially rich people come up with time .So I finally found out Jack Ma also had said :”i f you don’t put out more time and energy than others ,how can you achieve the success you want? If you do not do 996 when you are young ,when will you ?”I quite agree with the idea that young people should fight for success .But there are a lot of survival activities to do in a day ,I want to focus on how much time they take from us and what can we do with the rest of the time. As all we known ,There are 168 hours in a week .We sleep roughly seven-and-a-half and eight hours a day .so around 56 hours a week . maybe it is slightly different for someone . We do our personal things like eating and bathing and maybe looking after kids -about three hours a day .so around 21 hours a week .And if you are working a full time job ,so 40 hours a week , Oh! Maybe it is impossible for us at